Clean up Application layer commands/queries readability and correctness

Add missing AsNoTracking() on read-only queries, drop redundant
Update() calls on already-tracked entities, and fix inconsistent
formatting (stray spaces in generics, ternaries, and lambdas) across
the Albums/Tracks/PlayLists/Users command and query handlers.

backend/Core/Musify.Application/Albums/UpdateAlbum.cs

@@ -77,8 +77,6 @@ namespace Musify.Application.Albums
                 finalPictureKey = albumConfiguration.Routes.BuildOriginalPicturePath(request.UserId, pictureIntent.ObjectName);
             }
 
-            database.Albums.Update(album);
-
             if (pictureIntent != null && finalPictureKey != null)
             {
                 var publishResult = await PublishUpdateAlbumPictureSourceEventAsync(

backend/Core/Musify.Application/PlayLists/CreatePlayList.cs

@@ -106,7 +106,7 @@ namespace Musify.Application.PlayLists
             }, validation.Value);
         }
 
-        async Task<ErrorOr<Success>> PublishCreatePlayListEventAsync(
+        private async Task<ErrorOr<Success>> PublishCreatePlayListEventAsync(
             Guid playListId,
             UploadIntent pictureIntent,
             string finalPictureKey,

backend/Core/Musify.Application/PlayLists/UpdatePlayList.cs

@@ -85,8 +85,6 @@ namespace Musify.Application.PlayLists
                 finalPictureKey = playListConfiguration.Routes.BuildOriginalPicturePath(request.UserId, pictureIntent.ObjectName);
             }
 
-            database.PlayLists.Update(playListEntity);
-
             if (pictureIntent != null && finalPictureKey != null)
             {
                 var publishResult = await PublishUpdatePlayListPictureSourceEventAsync(
@@ -117,7 +115,7 @@ namespace Musify.Application.PlayLists
             return PlayListApplicationResponse.FromEntity(playListEntity, coverTrackIds);
         }
 
-        async Task<ErrorOr<Success>> PublishUpdatePlayListPictureSourceEventAsync(
+        private async Task<ErrorOr<Success>> PublishUpdatePlayListPictureSourceEventAsync(
             Guid playListId,
             UploadIntent pictureIntent,
             string finalPictureKey,

backend/Core/Musify.Application/Tracks/GetLastTrackListenedByUserId.cs

@@ -14,6 +14,7 @@ namespace Musify.Application.Tracks
         public async ValueTask<ErrorOr<TrackApplicationResponse>> Handle(GetLastTrackListenedByUserIdQuery query, CancellationToken cancellationToken)
         {
             var track = await database.ListeningHistories
+                .AsNoTracking()
                 .Include(t => t.Track.Owner)
                 .Include(t => t.Track.Tags)
                 .Where(t => t.UserId == query.UserId)

backend/Core/Musify.Application/Tracks/GetListeningHistory.cs

@@ -16,6 +16,7 @@ namespace Musify.Application.Tracks
         public async ValueTask<IEnumerable<TrackApplicationResponse>> Handle(GetListeningHistoryQuery query, CancellationToken cancellationToken)
         {
             var recentTrackIds = await database.ListeningHistories
+                .AsNoTracking()
                 .Where(l => l.UserId == query.UserId)
                 .GroupBy(l => l.TrackId)
                 .OrderByDescending(g => g.Max(l => l.ListenedAt))
@@ -24,6 +25,7 @@ namespace Musify.Application.Tracks
                 .ToListAsync(cancellationToken);
 
             var tracksById = await database.Tracks
+                .AsNoTracking()
                 .Include(t => t.Owner)
                 .Include(t => t.Tags)
                 .Where(t => recentTrackIds.Contains(t.Id))

backend/Core/Musify.Application/Users/GetListeningStats.cs

@@ -16,6 +16,7 @@ namespace Musify.Application.Users
             var weekAgo = DateTime.UtcNow.AddDays(-7);
 
             var thisWeekHistory = database.ListeningHistories
+                .AsNoTracking()
                 .Where(l => l.UserId == request.UserId && l.ListenedAt >= weekAgo);
 
             var tracksThisWeek = await thisWeekHistory
@@ -24,10 +25,11 @@ namespace Musify.Application.Users
                 .CountAsync(cancellationToken);
 
             var secondsThisWeek = await thisWeekHistory
-                .Join(database.Tracks, l => l.TrackId, t => t.Id, (l, t) => t.DurationSeconds)
+                .Join(database.Tracks.AsNoTracking(), l => l.TrackId, t => t.Id, (l, t) => t.DurationSeconds)
                 .SumAsync(cancellationToken);
 
             var listenedDates = await database.ListeningHistories
+                .AsNoTracking()
                 .Where(l => l.UserId == request.UserId)
                 .Select(l => l.ListenedAt.Date)
                 .Distinct()

backend/Core/Musify.Application/Users/GetUsers.cs

@@ -16,22 +16,22 @@ namespace Musify.Application.Users
     {
         public async ValueTask<ErrorOr<PaginatedResponse<UserApplicationResponse>>> Handle(GetUsersQuery request, CancellationToken cancellationToken)
         {
-            var user = database.Users
+            var usersQuery = database.Users
                 .AsNoTracking()
                 .AsQueryable();
 
             if (!string.IsNullOrEmpty(request.UsernameSearch))
             {
                 var normalizedUsername = request.UsernameSearch.Trim().ToUpperInvariant();
-                user = user.Where(u => u.NormalizedName.Contains(normalizedUsername));
+                usersQuery = usersQuery.Where(u => u.NormalizedName.Contains(normalizedUsername));
             }
 
-            var totalCount = await user.CountAsync(cancellationToken);
-            var pagedUser = await user
+            var totalCount = await usersQuery.CountAsync(cancellationToken);
+            var pagedUsers = await usersQuery
                 .Select(u => UserApplicationResponse.FromEntity(u))
                 .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
 
-            return PaginatedResponse<UserApplicationResponse>.FromPagedList(pagedUser);
+            return PaginatedResponse<UserApplicationResponse>.FromPagedList(pagedUsers);
         }
     }
 }