Remove YouTube integration from backend and deployment config

Drops the YouTube-backed second catalog source entirely: the
Local/External split on Track/Album collapses into single concrete
entities, Artist/TrackArtist/ExternalTrack/ExternalAlbum and the
YouTube service/download pipeline (yt-dlp, MassTransit consumer,
routing slip) are deleted, and mixes now source discovery only from
local listening history. Includes the RemoveYouTubeIntegration EF
Core migration and matching Worker/deploy/compose cleanup (no more
yt-dlp/python/deno in the Worker image, no thumbnail-cache/YtDlp
config sections).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/Core/Musify.Application/Albums/Responses/AlbumApplicationResponse.cs

@@ -4,15 +4,6 @@ using Musify.Application.Serialization;
 
 namespace Musify.Application.Albums.Responses
 {
-    // [JsonPolymorphic]/[JsonDerivedType] are required here, not optional: without them
-    // System.Text.Json serializes strictly by the declared CLR type at each call site
-    // (AlbumApplicationResponse, both as a bare return type and nested inside
-    // AlbumSearchItemResponse.Album), so an ExternalAlbumApplicationResponse instance would
-    // silently lose ExternalId/ThumbnailUrl on the wire. This also gives every response a
-    // "source" discriminator field for free, matching AlbumSearchItemResponse.Source.
-    [JsonPolymorphic(TypeDiscriminatorPropertyName = "source")]
-    [JsonDerivedType(typeof(AlbumApplicationResponse), typeDiscriminator: "Local")]
-    [JsonDerivedType(typeof(ExternalAlbumApplicationResponse), typeDiscriminator: "YouTube")]
     public record AlbumApplicationResponse(
         Guid Id,
         string Title,
@@ -30,7 +21,7 @@ namespace Musify.Application.Albums.Responses
         public const int CoverTrackCount = 4;
 
         public static AlbumApplicationResponse FromEntity(
-            UserAlbum album,
+            Album album,
             int trackCount,
             IReadOnlyList<Guid>? coverTrackIds = null)
         {
@@ -48,18 +39,5 @@ namespace Musify.Application.Albums.Responses
                 album.UpdatedAt,
                 coverTrackIds ?? []);
         }
-
-        public static AlbumApplicationResponse FromEntity(
-            Album album,
-            int trackCount,
-            IReadOnlyList<Guid>? coverTrackIds = null)
-        {
-            return album switch
-            {
-                ExternalAlbum externalAlbum => ExternalAlbumApplicationResponse.FromEntity(externalAlbum, trackCount, coverTrackIds),
-                UserAlbum userAlbum => FromEntity(userAlbum, trackCount, coverTrackIds),
-                _ => throw new NotSupportedException($"Unsupported album entity type '{album.GetType().Name}'.")
-            };
-        }
     }
 }

backend/Core/Musify.Application/Albums/Responses/AlbumSearchItemResponse.cs

@@ -1,22 +1,7 @@
-using Musify.Application.Contracts;
-using Musify.Domain.ValueObjects;
-
 namespace Musify.Application.Albums.Responses
 {
-    /// <summary>One item of a combined local/external album listing. Exactly one of
-    /// <see cref="Album"/> or <see cref="YouTubeAlbum"/> is populated: <see cref="Album"/> for
-    /// anything already in the catalog (locally created albums and external albums materialized
-    /// earlier), <see cref="YouTubeAlbum"/> for a live external search hit that hasn't been
-    /// materialized yet, so it has no album id.</summary>
-    public record AlbumSearchItemResponse(
-        TrackSource Source,
-        AlbumApplicationResponse? Album,
-        YouTubeAlbumResult? YouTubeAlbum)
+    public record AlbumSearchItemResponse(AlbumApplicationResponse Album)
     {
-        public static AlbumSearchItemResponse FromAlbum(AlbumApplicationResponse album) =>
-            new(album is ExternalAlbumApplicationResponse ? TrackSource.YouTube : TrackSource.Local, album, null);
-
-        public static AlbumSearchItemResponse FromYouTubeAlbum(YouTubeAlbumResult album) =>
-            new(TrackSource.YouTube, null, album);
+        public static AlbumSearchItemResponse FromAlbum(AlbumApplicationResponse album) => new(album);
     }
 }

backend/Core/Musify.Application/Albums/Responses/AlbumsSearchResponse.cs

@@ -1,11 +1,6 @@
 namespace Musify.Application.Albums.Responses
 {
-    /// <summary>Result of a combined albums listing/search: a page of local catalog albums
-    /// (user-created and previously materialized external albums), plus, when a search term was
-    /// given, live external hits appended after them. Pagination metadata (<see cref="PageNumber"/>,
-    /// <see cref="PageSize"/>, <see cref="PageCount"/>, <see cref="TotalItemCount"/>) describes only
-    /// the local page — the external source has no stable total, so its continuation is tracked
-    /// separately via <see cref="NextYoutubeContinuationToken"/>.</summary>
+    /// <summary>A page of the user's catalog albums (their own).</summary>
     public record AlbumsSearchResponse(
         IReadOnlyList<AlbumSearchItemResponse> Items,
         int PageNumber,
@@ -13,26 +8,5 @@ namespace Musify.Application.Albums.Responses
         int PageCount,
         int TotalItemCount,
         bool HasPreviousPage,
-        bool HasNextLocalPage,
-        string? NextYoutubeContinuationToken,
-        bool YoutubeUnavailable,
-        bool HasNextPage)
-    {
-        // HasNextPage is a real field (not a computed property) so it shows up as a required member
-        // of the generated OpenAPI schema, same as every other field here — a get-only property added
-        // outside the primary constructor gets reflected as optional instead, which is never true here.
-        public static AlbumsSearchResponse Create(
-            IReadOnlyList<AlbumSearchItemResponse> items,
-            int pageNumber,
-            int pageSize,
-            int pageCount,
-            int totalItemCount,
-            bool hasPreviousPage,
-            bool hasNextLocalPage,
-            string? nextYoutubeContinuationToken,
-            bool youtubeUnavailable) =>
-            new(items, pageNumber, pageSize, pageCount, totalItemCount, hasPreviousPage, hasNextLocalPage,
-                nextYoutubeContinuationToken, youtubeUnavailable,
-                HasNextPage: hasNextLocalPage || !string.IsNullOrEmpty(nextYoutubeContinuationToken));
-    }
+        bool HasNextPage);
 }

backend/Core/Musify.Application/Albums/Responses/ExternalAlbumApplicationResponse.cs

@@ -1,47 +0,0 @@
-using Musify.Domain.Entities;
-
-namespace Musify.Application.Albums.Responses
-{
-    public record ExternalAlbumApplicationResponse(
-        Guid Id,
-        string Title,
-        string? Description,
-        int? ReleaseYear,
-        long OwnerUserId,
-        int TrackCount,
-        string? SmallImageKeyName,
-        string? MediumImageKeyName,
-        string? LargeImageKeyName,
-        DateTime CreatedAt,
-        DateTime UpdatedAt,
-        IReadOnlyList<Guid> CoverTrackIds,
-        string ExternalId,
-        string? ThumbnailUrl)
-        : AlbumApplicationResponse(
-            Id, Title, Description, ReleaseYear, OwnerUserId, TrackCount,
-            SmallImageKeyName, MediumImageKeyName, LargeImageKeyName,
-            CreatedAt, UpdatedAt, CoverTrackIds)
-    {
-        public static ExternalAlbumApplicationResponse FromEntity(
-            ExternalAlbum album,
-            int trackCount,
-            IReadOnlyList<Guid>? coverTrackIds = null)
-        {
-            return new ExternalAlbumApplicationResponse(
-                album.Id,
-                album.Title,
-                album.Description,
-                album.ReleaseYear,
-                0,
-                trackCount,
-                album.Pictures?.SmallName,
-                album.Pictures?.MediumName,
-                album.Pictures?.LargeName,
-                album.CreatedAt,
-                album.UpdatedAt,
-                coverTrackIds ?? [],
-                album.ExternalId,
-                album.ThumbnailUrl);
-        }
-    }
-}