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).

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

@@ -1,37 +1,24 @@
 using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
-using Microsoft.Extensions.Logging;
 using Musify.Application.Tracks.Responses;
 using X.PagedList;
 using X.PagedList.EF;
 using Musify.Application.Contracts;
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.Tracks
 {
-    public record GetTracksQuery(string? Name, int PageNumber, int PageSize, string? YoutubeContinuationToken = null)
+    public record GetTracksQuery(string? Name, int PageNumber, int PageSize)
         : IQuery<ErrorOr<TracksSearchResponse>>;
 
-    public class GetTracksQueryHandler(
-        IDatabase database,
-        IYouTubeMusicService youTubeMusicService,
-        ILogger<GetTracksQueryHandler> logger)
+    public class GetTracksQueryHandler(IDatabase database)
         : IQueryHandler<GetTracksQuery, ErrorOr<TracksSearchResponse>>
     {
-        // Mirrors the web client's search-box debounce threshold: a query shorter than this is too
-        // likely to still be mid-keystroke to justify a live call to the YouTube Music API for every
-        // client that hits this endpoint.
-        private const int MinNameLengthForYouTubeSearch = 2;
-
         public async ValueTask<ErrorOr<TracksSearchResponse>> Handle(GetTracksQuery request, CancellationToken cancellationToken)
         {
             var tracksQuery = database.UserHasTracks
                 .AsNoTracking()
-                .Include(ut => ((ExternalTrack)ut.Track).TrackArtists)
-                    .ThenInclude(trackArtist => trackArtist.Artist)
-                .Include(ut => ((LocalTrack)ut.Track).Owner)
+                .Include(ut => ut.Track.Owner)
                 .AsQueryable();
 
             if (!string.IsNullOrEmpty(request.Name))
@@ -48,61 +35,18 @@ namespace Musify.Application.Tracks
                 .Select(t => new { t.Track, ListensCount = t.Track.ListeningHistories.Count })
                 .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
 
-            var localItems = pagedEntities
+            var items = pagedEntities
                 .Select(x => TrackSearchItemResponse.FromTrack(TrackApplicationResponse.FromEntity(x.Track, x.ListensCount)))
                 .ToList();
 
-            var knownVideoIds = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
-            foreach (var entry in pagedEntities)
-            {
-                if (entry.Track is ExternalTrack { Source: TrackSource.YouTube } external)
-                    knownVideoIds.Add(external.ExternalId);
-            }
-
-            var youtubeItems = new List<TrackSearchItemResponse>();
-            string? nextContinuationToken = null;
-            var youtubeUnavailable = false;
-
-            if (request.Name?.Trim().Length >= MinNameLengthForYouTubeSearch)
-                (youtubeItems, nextContinuationToken, youtubeUnavailable) =
-                    await SearchYouTubeAsync(request.Name, request.YoutubeContinuationToken, knownVideoIds, cancellationToken);
-
-            return TracksSearchResponse.Create(
-                [.. localItems, .. youtubeItems],
+            return new TracksSearchResponse(
+                items,
                 pagedEntities.PageNumber,
                 pagedEntities.PageSize,
                 pagedEntities.PageCount,
                 pagedEntities.TotalItemCount,
                 pagedEntities.HasPreviousPage,
-                pagedEntities.HasNextPage,
-                nextContinuationToken,
-                youtubeUnavailable);
-        }
-
-        private async Task<(List<TrackSearchItemResponse> Items, string? NextContinuationToken, bool Unavailable)> SearchYouTubeAsync(
-            string name,
-            string? continuationToken,
-            HashSet<string> knownVideoIds,
-            CancellationToken cancellationToken)
-        {
-            var searchResult = await youTubeMusicService.SearchSongsAsync(name, continuationToken ?? string.Empty, cancellationToken);
-            if (searchResult.IsError)
-            {
-                logger.LogInformation(
-                    "YouTube search unavailable while combining track results: {Error}", searchResult.FirstError.Description);
-                return ([], null, true);
-            }
-
-            var items = searchResult.Value.Items
-                .Where(song => knownVideoIds.Add(song.VideoId))
-                .Select(TrackSearchItemResponse.FromYouTubeSong)
-                .ToList();
-
-            var nextToken = string.IsNullOrEmpty(searchResult.Value.ContinuationToken)
-                ? null
-                : searchResult.Value.ContinuationToken;
-
-            return (items, nextToken, false);
+                pagedEntities.HasNextPage);
         }
     }
 }