feat(phase-16.3): light up anonId unique-listener layer

Mint a first-party localStorage anonId, thread it onto play/share beacons,
persist it via EventController, and add all-time distinct-listener counts
(site/track/release). Storage columns + indexes already existed from 16.1.

DeepDrftData/EventManager.cs

@@ -53,4 +53,48 @@ public class EventManager : IEventService
             return Result.CreateFailResult(e.Message);
         }
     }
+
+    public async Task<ResultContainer<int>> GetDistinctListenerCount(CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            var count = await _repository.CountDistinctListenersAsync(cancellationToken);
+            return ResultContainer<int>.CreatePassResult(count);
+        }
+        catch (Exception e)
+        {
+            _logger.LogError(e, "Failed to count distinct listeners");
+            return ResultContainer<int>.CreateFailResult(e.Message);
+        }
+    }
+
+    public async Task<ResultContainer<int>> GetDistinctListenerCountForTrack(
+        string trackEntryKey, CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            var count = await _repository.CountDistinctListenersForTrackAsync(trackEntryKey, cancellationToken);
+            return ResultContainer<int>.CreatePassResult(count);
+        }
+        catch (Exception e)
+        {
+            _logger.LogError(e, "Failed to count distinct listeners for track {TrackEntryKey}", trackEntryKey);
+            return ResultContainer<int>.CreateFailResult(e.Message);
+        }
+    }
+
+    public async Task<ResultContainer<int>> GetDistinctListenerCountForRelease(
+        long releaseId, CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            var count = await _repository.CountDistinctListenersForReleaseAsync(releaseId, cancellationToken);
+            return ResultContainer<int>.CreatePassResult(count);
+        }
+        catch (Exception e)
+        {
+            _logger.LogError(e, "Failed to count distinct listeners for release {ReleaseId}", releaseId);
+            return ResultContainer<int>.CreateFailResult(e.Message);
+        }
+    }
 }