feat: Stream Now instant-play of a random track from the nav button

DeepDrftData/Repositories/TrackRepository.cs

@@ -25,6 +25,25 @@ public class TrackRepository : Repository<DeepDrftContext, TrackEntity>
     public async Task<TrackEntity?> GetByEntryKeyAsync(string entryKey)
         => await _context.Tracks.FirstOrDefaultAsync(t => t.EntryKey == entryKey);
 
+    // Picks one track uniformly at random. Two round-trips (count, then a single offset row)
+    // rather than ORDER BY random() so the database never sorts the whole table — the catalogue
+    // is small today but this keeps the cost flat as it grows. Returns null when empty so the
+    // service surfaces a valid empty-library state, not an error. Queries the DbSet directly,
+    // mirroring GetByEntryKeyAsync, since the base Repository<> exposes only id-based reads.
+    public async Task<TrackEntity?> GetRandomAsync(CancellationToken cancellationToken = default)
+    {
+        var count = await _context.Tracks.CountAsync(cancellationToken);
+        if (count == 0)
+            return null;
+
+        var index = Random.Shared.Next(count);
+        return await _context.Tracks
+            .OrderBy(t => t.Id)
+            .Skip(index)
+            .Take(1)
+            .FirstOrDefaultAsync(cancellationToken);
+    }
+
     protected override void UpdateEntity(TrackEntity target, TrackEntity source)
     {
         base.UpdateEntity(target, source); // copies CreatedAt, UpdatedAt, IsDeleted