feat(backend): add Artist entity and track ownership

Track.Artist was a plain string snapshot with no identity, and
UserHasTrack doubled as both "in my library" and "I own this",
conflating collection membership with administrative ownership.

Introduce Artist/TrackArtist to give artist credits their own
identity (needed so YouTube tracks with multiple credited artists,
and future renames, can be modeled), and Track.OwnerUserId to
represent ownership explicitly (local tracks only, enforced by a
check constraint). CreateTrack now provisions the uploader's Artist
row and links it via TrackArtist; DeleteTrack authorizes against
OwnerUserId instead of any UserHasTrack row.

backend/Musify.Application/Contracts/IDatabase.cs

@@ -11,6 +11,10 @@ namespace Musify.Application.Contracts
 
         DbSet<Track> Tracks { get; }
 
+        DbSet<Artist> Artists { get; }
+
+        DbSet<TrackArtist> TrackArtists { get; }
+
         DbSet<UserHasTrack> UserHasTracks { get; }
 
         DbSet<PlayListHasTrack> PlayListHasTracks { get; }

backend/Musify.Application/Tracks/CreateTrack.cs

@@ -32,9 +32,9 @@ namespace Musify.Application.Tracks
     {
         public async ValueTask<ErrorOr<TrackApplicationResponse>> Handle(CreateTrackCommand request, CancellationToken cancellationToken)
         {
-            var userExists = await database.Users.AsNoTracking()
-                .AnyAsync(u => u.Id == request.UserId, cancellationToken);
-            if (!userExists)
+            var user = await database.Users.AsNoTracking()
+                .SingleOrDefaultAsync(u => u.Id == request.UserId, cancellationToken);
+            if (user is null)
             {
                 logger.LogWarning("User {UserId} not found", request.UserId);
                 return Error.NotFound(description: $"User {request.UserId} not found");
@@ -59,10 +59,14 @@ namespace Musify.Application.Tracks
             var finalAudioKey = trackConfiguration.Routes.BuildOriginalAudioPath(request.UserId, audioIntent.ObjectName);
             var audioProcessedFolderKey = trackConfiguration.Routes.BuildProcessedAudioPath(Guid.NewGuid().ToString());
 
+            var artist = await GetOrCreateUserArtistAsync(user, cancellationToken);
+
             var trackEntity = new Track
             {
                 Title = request.Title,
                 NormalizedTitle = request.Title.ToUpperInvariant(),
+                Artist = user.Name,
+                OwnerUserId = user.Id,
                 OriginalPictureName = pictureIntent.ObjectName,
                 OriginalAudioName = audioIntent.ObjectName,
                 SmallPictureName = trackConfiguration.Routes.PresetSmallPicture,
@@ -74,6 +78,13 @@ namespace Musify.Application.Tracks
 
             await database.Tracks.AddAsync(trackEntity, cancellationToken);
 
+            await database.TrackArtists.AddAsync(new TrackArtist
+            {
+                TrackId = trackEntity.Id,
+                ArtistId = artist.Id,
+                Position = 0
+            }, cancellationToken);
+
             await database.UserHasTracks.AddAsync(new UserHasTrack
             {
                 UserId = request.UserId,
@@ -125,5 +136,32 @@ namespace Musify.Application.Tracks
 
             return TrackApplicationResponse.FromEntity(trackEntity, listensCount: 0);
         }
+
+        private async Task<Artist> GetOrCreateUserArtistAsync(User user, CancellationToken cancellationToken)
+        {
+            var existing = await database.Artists.SingleOrDefaultAsync(a => a.UserId == user.Id, cancellationToken);
+            if (existing is not null)
+                return existing;
+
+            var artist = new Artist
+            {
+                Name = user.Name,
+                NormalizedName = user.NormalizedName,
+                UserId = user.Id
+            };
+
+            await database.Artists.AddAsync(artist, cancellationToken);
+
+            try
+            {
+                await database.SaveChangesAsync(cancellationToken);
+                return artist;
+            }
+            catch (DbUpdateException)
+            {
+                database.Artists.Remove(artist);
+                return await database.Artists.SingleAsync(a => a.UserId == user.Id, cancellationToken);
+            }
+        }
     }
 }

backend/Musify.Application/Tracks/DeleteTrack.cs

@@ -28,10 +28,7 @@ namespace Musify.Application.Tracks
                 return Error.NotFound();
             }
 
-            var isOwner = await database.UserHasTracks
-                .AsNoTracking()
-                .AnyAsync(ut => ut.TrackId == request.TrackId && ut.UserId == request.UserId, cancellationToken);
-            if (!isOwner)
+            if (track.OwnerUserId != request.UserId)
             {
                 logger.LogWarning("User {UserId} unauthorized to delete track {TrackId}", request.UserId, request.TrackId);
                 return Error.Unauthorized();

backend/Musify.Application/Tracks/Responses/TrackApplicationResponse.cs

@@ -12,6 +12,7 @@ namespace Musify.Application.Tracks.Responses
         ProcessingStatus AudioStatus,
         int Duration,
         int ListensCount,
+        long? OwnerUserId,
         DateTime CreatedAt,
         DateTime UpdatedAt)
     {
@@ -25,6 +26,7 @@ namespace Musify.Application.Tracks.Responses
                 track.AudioTranscodeProcessingStatus,
                 track.Duration,
                 listensCount,
+                track.OwnerUserId,
                 track.CreatedAt,
                 track.UpdatedAt);
     }

backend/Musify.Domain/Entities/Artist.cs

@@ -0,0 +1,37 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+using Musify.Domain.Abstractions;
+
+namespace Musify.Domain.Entities
+{
+#pragma warning disable CS8618
+    public class Artist : IAuditable
+    {
+        [Key]
+        public Guid Id { get; set; } = Guid.NewGuid();
+
+        [Required]
+        [MaxLength(200)]
+        public required string Name { get; set; }
+
+        [Required]
+        [MaxLength(200)]
+        public required string NormalizedName { get; set; }
+
+        public long? UserId { get; set; }
+
+        [MaxLength(64)]
+        public string? ExternalId { get; set; }
+
+        [Required]
+        public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+
+        [Required]
+        public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
+
+        [ForeignKey(nameof(UserId)) ]
+        public User? User { get; set; }
+
+        public ICollection<TrackArtist> TrackArtists { get; set; } = new List<TrackArtist>();
+    }
+}

backend/Musify.Domain/Entities/Track.cs

@@ -26,6 +26,8 @@ namespace Musify.Domain.Entities
         [MaxLength(200)]
         public string? Artist { get; set; }
 
+        public long? OwnerUserId { get; set; }
+
         [Required]
         public TrackSource Source { get; set; } = TrackSource.Local;
 
@@ -73,12 +75,17 @@ namespace Musify.Domain.Entities
         [Required]
         public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
 
+        [ForeignKey(nameof(OwnerUserId))]
+        public User? Owner { get; set; }
+
         public ICollection<UserHasTrack> UserTracks { get; set; } = new List<UserHasTrack>();
 
         public ICollection<PlayListHasTrack> PlayListTracks { get; set; } = new List<PlayListHasTrack>();
 
         public ICollection<ListeningHistory> ListeningHistories { get; set; } = new List<ListeningHistory>();
 
+        public ICollection<TrackArtist> TrackArtists { get; set; } = new List<TrackArtist>();
+
         [NotMapped]
         [MemberNotNullWhen(true, nameof(SmallPictureName)) ]
         [MemberNotNullWhen(true, nameof(MediumPictureName)) ]

backend/Musify.Domain/Entities/TrackArtist.cs

@@ -0,0 +1,25 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Musify.Domain.Entities
+{
+#pragma warning disable CS8618
+    [Table("TrackArtist")]
+    public class TrackArtist
+    {
+        [Required]
+        public required Guid TrackId { get; set; }
+
+        [Required]
+        public required Guid ArtistId { get; set; }
+
+        [Required]
+        public int Position { get; set; } = 0;
+
+        [ForeignKey(nameof(TrackId)) ]
+        public Track Track { get; set; }
+
+        [ForeignKey(nameof(ArtistId)) ]
+        public Artist Artist { get; set; }
+    }
+}

backend/Musify.Infrastructure/Persistence/Database.cs

@@ -34,6 +34,45 @@ namespace Musify.Infrastructure.Persistence
                 .HasIndex(track => new { track.Source, track.ExternalId })
                 .IsUnique();
 
+            modelBuilder.Entity<Track>()
+                .HasOne(track => track.Owner)
+                .WithMany()
+                .HasForeignKey(track => track.OwnerUserId)
+                .OnDelete(DeleteBehavior.Restrict);
+
+            modelBuilder.Entity<Track>()
+                .ToTable(t => t.HasCheckConstraint(
+                    "CK_Tracks_OwnerUserId_Source",
+                    "(\"OwnerUserId\" IS NOT NULL) = (\"Source\" = 0)"));
+
+            modelBuilder.Entity<TrackArtist>()
+                .HasKey(trackArtist => new { trackArtist.TrackId, trackArtist.ArtistId });
+
+            modelBuilder.Entity<TrackArtist>()
+                .HasOne(trackArtist => trackArtist.Track)
+                .WithMany(track => track.TrackArtists)
+                .HasForeignKey(trackArtist => trackArtist.TrackId)
+                .OnDelete(DeleteBehavior.Cascade);
+
+            modelBuilder.Entity<TrackArtist>()
+                .HasOne(trackArtist => trackArtist.Artist)
+                .WithMany(artist => artist.TrackArtists)
+                .HasForeignKey(trackArtist => trackArtist.ArtistId)
+                .OnDelete(DeleteBehavior.Cascade);
+
+            modelBuilder.Entity<Artist>()
+                .HasIndex(artist => artist.UserId)
+                .IsUnique();
+
+            modelBuilder.Entity<Artist>()
+                .HasIndex(artist => artist.ExternalId)
+                .IsUnique();
+
+            modelBuilder.Entity<Artist>()
+                .HasIndex(artist => artist.NormalizedName)
+                .IsUnique()
+                .HasFilter("\"ExternalId\" IS NULL AND \"UserId\" IS NULL");
+
             var playListProcessing = modelBuilder.Entity<PlayListProcessingState>();
             playListProcessing.HasKey(state => state.CorrelationId);
             playListProcessing.Property(state => state.CorrelationId).ValueGeneratedNever();
@@ -44,6 +83,10 @@ namespace Musify.Infrastructure.Persistence
 
         public DbSet<Track> Tracks => Set<Track>();
 
+        public DbSet<Artist> Artists => Set<Artist>();
+
+        public DbSet<TrackArtist> TrackArtists => Set<TrackArtist>();
+
         public DbSet<PlayList> PlayLists => Set<PlayList>();
 
         public DbSet<UserHasTrack> UserHasTracks => Set<UserHasTrack>();

backend/Musify.Infrastructure/Persistence/Migrations/20260716214752_AddArtistsAndTrackOwnership.Designer.cs

@@ -0,0 +1,826 @@
+// <auto-generated />
+using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Musify.Infrastructure.Persistence;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace Musify.Infrastructure.Persistence.Migrations
+{
+    [DbContext(typeof(Database))]
+    [Migration("20260716214752_AddArtistsAndTrackOwnership")]
+    partial class AddArtistsAndTrackOwnership
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "10.0.8")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("MassTransit.EntityFrameworkCoreIntegration.InboxState", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<DateTime?>("Consumed")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid>("ConsumerId")
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTime?>("Delivered")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<DateTime?>("ExpirationTime")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<long?>("LastSequenceNumber")
+                        .HasColumnType("bigint");
+
+                    b.Property<Guid>("LockId")
+                        .HasColumnType("uuid");
+
+                    b.Property<Guid>("MessageId")
+                        .HasColumnType("uuid");
+
+                    b.Property<int>("ReceiveCount")
+                        .HasColumnType("integer");
+
+                    b.Property<DateTime>("Received")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<byte[]>("RowVersion")
+                        .IsConcurrencyToken()
+                        .ValueGeneratedOnAddOrUpdate()
+                        .HasColumnType("bytea");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Delivered");
+
+                    b.ToTable("InboxState");
+                });
+
+            modelBuilder.Entity("MassTransit.EntityFrameworkCoreIntegration.OutboxMessage", b =>
+                {
+                    b.Property<long>("SequenceNumber")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("SequenceNumber"));
+
+                    b.Property<string>("Body")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("ContentType")
+                        .IsRequired()
+                        .HasMaxLength(256)
+                        .HasColumnType("character varying(256)");
+
+                    b.Property<Guid?>("ConversationId")
+                        .HasColumnType("uuid");
+
+                    b.Property<Guid?>("CorrelationId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("DestinationAddress")
+                        .HasMaxLength(256)
+                        .HasColumnType("character varying(256)");
+
+                    b.Property<DateTime?>("EnqueueTime")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<DateTime?>("ExpirationTime")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("FaultAddress")
+                        .HasMaxLength(256)
+                        .HasColumnType("character varying(256)");
+
+                    b.Property<string>("Headers")
+                        .HasColumnType("text");
+
+                    b.Property<Guid?>("InboxConsumerId")
+                        .HasColumnType("uuid");
+
+                    b.Property<Guid?>("InboxMessageId")
+                        .HasColumnType("uuid");
+
+                    b.Property<Guid?>("InitiatorId")
+                        .HasColumnType("uuid");
+
+                    b.Property<Guid>("MessageId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("MessageType")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<Guid?>("OutboxId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Properties")
+                        .HasColumnType("text");
+
+                    b.Property<Guid?>("RequestId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("ResponseAddress")
+                        .HasMaxLength(256)
+                        .HasColumnType("character varying(256)");
+
+                    b.Property<DateTime>("SentTime")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("SourceAddress")
+                        .HasMaxLength(256)
+                        .HasColumnType("character varying(256)");
+
+                    b.HasKey("SequenceNumber");
+
+                    b.HasIndex("EnqueueTime");
+
+                    b.HasIndex("ExpirationTime");
+
+                    b.HasIndex("OutboxId", "SequenceNumber")
+                        .IsUnique();
+
+                    b.HasIndex("InboxMessageId", "InboxConsumerId", "SequenceNumber")
+                        .IsUnique();
+
+                    b.ToTable("OutboxMessage");
+                });
+
+            modelBuilder.Entity("MassTransit.EntityFrameworkCoreIntegration.OutboxState", b =>
+                {
+                    b.Property<Guid>("OutboxId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTime>("Created")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<DateTime?>("Delivered")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<long?>("LastSequenceNumber")
+                        .HasColumnType("bigint");
+
+                    b.Property<Guid>("LockId")
+                        .HasColumnType("uuid");
+
+                    b.Property<byte[]>("RowVersion")
+                        .IsConcurrencyToken()
+                        .ValueGeneratedOnAddOrUpdate()
+                        .HasColumnType("bytea");
+
+                    b.HasKey("OutboxId");
+
+                    b.HasIndex("Created");
+
+                    b.ToTable("OutboxState");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.Artist", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("ExternalId")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<string>("NormalizedName")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<long?>("UserId")
+                        .HasColumnType("bigint");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ExternalId")
+                        .IsUnique();
+
+                    b.HasIndex("NormalizedName")
+                        .IsUnique()
+                        .HasFilter("\"ExternalId\" IS NULL AND \"UserId\" IS NULL");
+
+                    b.HasIndex("UserId")
+                        .IsUnique();
+
+                    b.ToTable("Artists");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.ListeningHistory", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTime>("ListenedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid>("TrackId")
+                        .HasColumnType("uuid");
+
+                    b.Property<long>("UserId")
+                        .HasColumnType("bigint");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("TrackId");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("ListeningHistory");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.PlayList", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Description")
+                        .IsRequired()
+                        .HasMaxLength(256)
+                        .HasColumnType("character varying(256)");
+
+                    b.Property<string>("LargePictureName")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<int>("LifeCycleStatus")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("MediumPictureName")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.Property<string>("NormalizedName")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.Property<string>("OriginalPictureName")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<string>("SmallPictureName")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<long>("UserId")
+                        .HasColumnType("bigint");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("PlayLists");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.PlayListHasTrack", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTime>("AddedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid>("PlayListId")
+                        .HasColumnType("uuid");
+
+                    b.Property<int>("Position")
+                        .HasColumnType("integer");
+
+                    b.Property<Guid>("TrackId")
+                        .HasColumnType("uuid");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("PlayListId");
+
+                    b.HasIndex("TrackId");
+
+                    b.ToTable("PlayListHasTrack");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.Track", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Artist")
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<string>("AudioFolderName")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<int>("AudioTranscodeProcessingStatus")
+                        .HasColumnType("integer");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<bool>("DownloadRequested")
+                        .HasColumnType("boolean");
+
+                    b.Property<int>("Duration")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("ExternalId")
+                        .HasMaxLength(16)
+                        .HasColumnType("character varying(16)");
+
+                    b.Property<string>("LargePictureName")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<DateTime?>("LastRetryAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("LifeCycleStatus")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("MediumPictureName")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<string>("NormalizedTitle")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.Property<string>("OriginalAudioName")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<string>("OriginalPictureName")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<long?>("OwnerUserId")
+                        .HasColumnType("bigint");
+
+                    b.Property<int>("PicturesProcessingStatus")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("RetryCount")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("SmallPictureName")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<int>("Source")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("Title")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("OwnerUserId");
+
+                    b.HasIndex("Source", "ExternalId")
+                        .IsUnique();
+
+                    b.ToTable("Tracks", t =>
+                        {
+                            t.HasCheckConstraint("CK_Tracks_OwnerUserId_Source", "(\"OwnerUserId\" IS NOT NULL) = (\"Source\" = 0)");
+                        });
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.TrackArtist", b =>
+                {
+                    b.Property<Guid>("TrackId")
+                        .HasColumnType("uuid");
+
+                    b.Property<Guid>("ArtistId")
+                        .HasColumnType("uuid");
+
+                    b.Property<int>("Position")
+                        .HasColumnType("integer");
+
+                    b.HasKey("TrackId", "ArtistId");
+
+                    b.HasIndex("ArtistId");
+
+                    b.ToTable("TrackArtist");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.Upload", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Bucket")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("ContentType")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<DateTime>("CreatedTime")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Key")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<int>("State")
+                        .HasColumnType("integer");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("Upload");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.UploadIntent", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Bucket")
+                        .IsRequired()
+                        .HasMaxLength(128)
+                        .HasColumnType("character varying(128)");
+
+                    b.Property<string>("ContentType")
+                        .IsRequired()
+                        .HasMaxLength(128)
+                        .HasColumnType("character varying(128)");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<long?>("ExpectedSizeBytes")
+                        .HasColumnType("bigint");
+
+                    b.Property<DateTime>("ExpiresAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Key")
+                        .IsRequired()
+                        .HasMaxLength(512)
+                        .HasColumnType("character varying(512)");
+
+                    b.Property<string>("ObjectName")
+                        .IsRequired()
+                        .HasMaxLength(128)
+                        .HasColumnType("character varying(128)");
+
+                    b.Property<int>("Purpose")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("Status")
+                        .HasColumnType("integer");
+
+                    b.Property<long>("UserId")
+                        .HasColumnType("bigint");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("UploadIntents");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.User", b =>
+                {
+                    b.Property<long>("Id")
+                        .HasColumnType("bigint");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("FirstName")
+                        .HasMaxLength(48)
+                        .HasColumnType("character varying(48)");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(48)
+                        .HasColumnType("character varying(48)");
+
+                    b.Property<string>("NormalizedName")
+                        .IsRequired()
+                        .HasMaxLength(48)
+                        .HasColumnType("character varying(48)");
+
+                    b.Property<string>("ProfilePictureUrl")
+                        .HasMaxLength(2048)
+                        .HasColumnType("character varying(2048)");
+
+                    b.Property<string>("SecondName")
+                        .HasMaxLength(48)
+                        .HasColumnType("character varying(48)");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("User");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.UserHasTrack", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<Guid>("TrackId")
+                        .HasColumnType("uuid");
+
+                    b.Property<long>("UserId")
+                        .HasColumnType("bigint");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("TrackId");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("UserHasTrack");
+                });
+
+            modelBuilder.Entity("Musify.Infrastructure.MassTransit.Sagas.PlayListProcessingState", b =>
+                {
+                    b.Property<Guid>("CorrelationId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Bucket")
+                        .HasColumnType("text");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("CurrentState")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<string>("PictureKey")
+                        .HasColumnType("text");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("CorrelationId");
+
+                    b.ToTable("PlayListProcessingState");
+                });
+
+            modelBuilder.Entity("Musify.Infrastructure.MassTransit.Sagas.TrackProcessingState", b =>
+                {
+                    b.Property<Guid>("CorrelationId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("AudioKey")
+                        .HasColumnType("text");
+
+                    b.Property<bool>("AudioProcessed")
+                        .HasColumnType("boolean");
+
+                    b.Property<string>("Bucket")
+                        .HasColumnType("text");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("CurrentState")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<string>("PictureKey")
+                        .HasColumnType("text");
+
+                    b.Property<bool>("PictureProcessed")
+                        .HasColumnType("boolean");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("CorrelationId");
+
+                    b.ToTable("TrackProcessingState");
+                });
+
+            modelBuilder.Entity("MassTransit.EntityFrameworkCoreIntegration.OutboxMessage", b =>
+                {
+                    b.HasOne("MassTransit.EntityFrameworkCoreIntegration.OutboxState", null)
+                        .WithMany()
+                        .HasForeignKey("OutboxId");
+
+                    b.HasOne("MassTransit.EntityFrameworkCoreIntegration.InboxState", null)
+                        .WithMany()
+                        .HasForeignKey("InboxMessageId", "InboxConsumerId")
+                        .HasPrincipalKey("MessageId", "ConsumerId");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.Artist", b =>
+                {
+                    b.HasOne("Musify.Domain.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId");
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.ListeningHistory", b =>
+                {
+                    b.HasOne("Musify.Domain.Entities.Track", "Track")
+                        .WithMany("ListeningHistories")
+                        .HasForeignKey("TrackId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("Musify.Domain.Entities.User", "User")
+                        .WithMany("ListeningHistories")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Track");
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.PlayList", b =>
+                {
+                    b.HasOne("Musify.Domain.Entities.User", "User")
+                        .WithMany("PlayLists")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.PlayListHasTrack", b =>
+                {
+                    b.HasOne("Musify.Domain.Entities.PlayList", "PlayList")
+                        .WithMany("PlayListTracks")
+                        .HasForeignKey("PlayListId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("Musify.Domain.Entities.Track", "Track")
+                        .WithMany("PlayListTracks")
+                        .HasForeignKey("TrackId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("PlayList");
+
+                    b.Navigation("Track");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.Track", b =>
+                {
+                    b.HasOne("Musify.Domain.Entities.User", "Owner")
+                        .WithMany()
+                        .HasForeignKey("OwnerUserId")
+                        .OnDelete(DeleteBehavior.Restrict);
+
+                    b.Navigation("Owner");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.TrackArtist", b =>
+                {
+                    b.HasOne("Musify.Domain.Entities.Artist", "Artist")
+                        .WithMany("TrackArtists")
+                        .HasForeignKey("ArtistId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("Musify.Domain.Entities.Track", "Track")
+                        .WithMany("TrackArtists")
+                        .HasForeignKey("TrackId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Artist");
+
+                    b.Navigation("Track");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.UploadIntent", b =>
+                {
+                    b.HasOne("Musify.Domain.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.UserHasTrack", b =>
+                {
+                    b.HasOne("Musify.Domain.Entities.Track", "Track")
+                        .WithMany("UserTracks")
+                        .HasForeignKey("TrackId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("Musify.Domain.Entities.User", "User")
+                        .WithMany("UserTracks")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Track");
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.Artist", b =>
+                {
+                    b.Navigation("TrackArtists");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.PlayList", b =>
+                {
+                    b.Navigation("PlayListTracks");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.Track", b =>
+                {
+                    b.Navigation("ListeningHistories");
+
+                    b.Navigation("PlayListTracks");
+
+                    b.Navigation("TrackArtists");
+
+                    b.Navigation("UserTracks");
+                });
+
+            modelBuilder.Entity("Musify.Domain.Entities.User", b =>
+                {
+                    b.Navigation("ListeningHistories");
+
+                    b.Navigation("PlayLists");
+
+                    b.Navigation("UserTracks");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

backend/Musify.Infrastructure/Persistence/Migrations/20260716214752_AddArtistsAndTrackOwnership.cs

@@ -0,0 +1,174 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Musify.Infrastructure.Persistence.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddArtistsAndTrackOwnership : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<long>(
+                name: "OwnerUserId",
+                table: "Tracks",
+                type: "bigint",
+                nullable: true);
+
+            migrationBuilder.CreateTable(
+                name: "Artists",
+                columns: table => new
+                {
+                    Id = table.Column<Guid>(type: "uuid", nullable: false),
+                    Name = table.Column<string>(type: "character varying(200)", maxLength: 200, nullable: false),
+                    NormalizedName = table.Column<string>(type: "character varying(200)", maxLength: 200, nullable: false),
+                    UserId = table.Column<long>(type: "bigint", nullable: true),
+                    ExternalId = table.Column<string>(type: "character varying(64)", maxLength: 64, nullable: true),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    UpdatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_Artists", x => x.Id);
+                    table.ForeignKey(
+                        name: "FK_Artists_User_UserId",
+                        column: x => x.UserId,
+                        principalTable: "User",
+                        principalColumn: "Id");
+                });
+
+            migrationBuilder.CreateTable(
+                name: "TrackArtist",
+                columns: table => new
+                {
+                    TrackId = table.Column<Guid>(type: "uuid", nullable: false),
+                    ArtistId = table.Column<Guid>(type: "uuid", nullable: false),
+                    Position = table.Column<int>(type: "integer", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_TrackArtist", x => new { x.TrackId, x.ArtistId });
+                    table.ForeignKey(
+                        name: "FK_TrackArtist_Artists_ArtistId",
+                        column: x => x.ArtistId,
+                        principalTable: "Artists",
+                        principalColumn: "Id",
+                        onDelete: ReferentialAction.Cascade);
+                    table.ForeignKey(
+                        name: "FK_TrackArtist_Tracks_TrackId",
+                        column: x => x.TrackId,
+                        principalTable: "Tracks",
+                        principalColumn: "Id",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Tracks_OwnerUserId",
+                table: "Tracks",
+                column: "OwnerUserId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Artists_ExternalId",
+                table: "Artists",
+                column: "ExternalId",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Artists_NormalizedName",
+                table: "Artists",
+                column: "NormalizedName",
+                unique: true,
+                filter: "\"ExternalId\" IS NULL AND \"UserId\" IS NULL");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Artists_UserId",
+                table: "Artists",
+                column: "UserId",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_TrackArtist_ArtistId",
+                table: "TrackArtist",
+                column: "ArtistId");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Tracks_User_OwnerUserId",
+                table: "Tracks",
+                column: "OwnerUserId",
+                principalTable: "User",
+                principalColumn: "Id",
+                onDelete: ReferentialAction.Restrict);
+
+            migrationBuilder.Sql(
+                """
+                UPDATE "Tracks" t SET "OwnerUserId" = ut."UserId"
+                FROM (SELECT "TrackId", MIN("UserId") AS "UserId" FROM "UserHasTrack" GROUP BY "TrackId") ut
+                WHERE t."Source" = 0 AND ut."TrackId" = t."Id";
+                """);
+
+            migrationBuilder.Sql(
+                """
+                INSERT INTO "Artists" ("Id", "Name", "NormalizedName", "UserId", "ExternalId", "CreatedAt", "UpdatedAt")
+                SELECT gen_random_uuid(), u."Name", u."NormalizedName", u."Id", NULL, now(), now()
+                FROM "User" u
+                WHERE EXISTS (SELECT 1 FROM "Tracks" t WHERE t."OwnerUserId" = u."Id");
+                """);
+
+            migrationBuilder.Sql(
+                """
+                INSERT INTO "Artists" ("Id", "Name", "NormalizedName", "UserId", "ExternalId", "CreatedAt", "UpdatedAt")
+                SELECT gen_random_uuid(), s."Artist", upper(s."Artist"), NULL, NULL, now(), now()
+                FROM (SELECT DISTINCT "Artist" FROM "Tracks" WHERE "Source" = 1 AND "Artist" IS NOT NULL) s;
+                """);
+
+            migrationBuilder.Sql(
+                """
+                INSERT INTO "TrackArtist" ("TrackId", "ArtistId", "Position")
+                SELECT t."Id", a."Id", 0 FROM "Tracks" t
+                JOIN "Artists" a ON a."UserId" = t."OwnerUserId"
+                WHERE t."Source" = 0;
+                """);
+
+            migrationBuilder.Sql(
+                """
+                INSERT INTO "TrackArtist" ("TrackId", "ArtistId", "Position")
+                SELECT t."Id", a."Id", 0 FROM "Tracks" t
+                JOIN "Artists" a ON a."UserId" IS NULL AND a."ExternalId" IS NULL AND a."Name" = t."Artist"
+                WHERE t."Source" = 1 AND t."Artist" IS NOT NULL;
+                """);
+
+            migrationBuilder.AddCheckConstraint(
+                name: "CK_Tracks_OwnerUserId_Source",
+                table: "Tracks",
+                sql: "(\"OwnerUserId\" IS NOT NULL) = (\"Source\" = 0)");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_Tracks_User_OwnerUserId",
+                table: "Tracks");
+
+            migrationBuilder.DropTable(
+                name: "TrackArtist");
+
+            migrationBuilder.DropTable(
+                name: "Artists");
+
+            migrationBuilder.DropIndex(
+                name: "IX_Tracks_OwnerUserId",
+                table: "Tracks");
+
+            migrationBuilder.DropCheckConstraint(
+                name: "CK_Tracks_OwnerUserId_Source",
+                table: "Tracks");
+
+            migrationBuilder.DropColumn(
+                name: "OwnerUserId",
+                table: "Tracks");
+        }
+    }
+}