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

DeepDrftData/ITrackService.cs

@@ -13,6 +13,12 @@ public interface ITrackService
 {
     Task<ResultContainer<TrackDto?>> GetById(long id);
     Task<ResultContainer<TrackDto?>> GetByEntryKey(string entryKey);
+
+    /// <summary>
+    /// Returns a single track chosen uniformly at random, or null when the library is empty
+    /// (a valid state, not a failure). Backs the public "Stream Now" instant-play feature.
+    /// </summary>
+    Task<ResultContainer<TrackDto?>> GetRandom(CancellationToken cancellationToken = default);
     Task<ResultContainer<List<TrackDto>>> GetAll();
     Task<ResultContainer<PagedResult<TrackDto>>> GetPaged(int pageNumber, int pageSize, string? sortColumn, bool sortDescending, CancellationToken cancellationToken = default);
     Task<ResultContainer<TrackDto>> Create(TrackDto newTrack);

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

DeepDrftData/TrackManager.cs

@@ -62,6 +62,22 @@ public class TrackManager
         }
     }
 
+    // No base-name conflict, so this is a plain public method. Mirrors the nullable-on-empty
+    // shape of GetById: pass with null when the library has no tracks.
+    public async Task<ResultContainer<TrackDto?>> GetRandom(CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            var entity = await Repository.GetRandomAsync(cancellationToken);
+            return ResultContainer<TrackDto?>.CreatePassResult(
+                entity is null ? null : TrackConverter.Convert(entity));
+        }
+        catch (Exception e)
+        {
+            return ResultContainer<TrackDto?>.CreateFailResult(e.Message);
+        }
+    }
+
     public async Task<ResultContainer<List<TrackDto>>> GetAll()
     {
         try