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.

DeepDrftPublic.Client/Controls/AudioPlayerProvider.razor.cs

@@ -12,6 +12,7 @@ public partial class AudioPlayerProvider : ComponentBase, IAsyncDisposable
     [Inject] public required ILogger<StreamingAudioPlayerService> Logger { get; set; }
     [Inject] public required BeaconInterop Beacon { get; set; }
     [Inject] public required IPlayEventSink PlayEventSink { get; set; }
+    [Inject] public required IAnonIdProvider AnonId { get; set; }
 
     private IStreamingPlayerService? _audioPlayerService;
     private QueueService? _queueService;
@@ -50,6 +51,20 @@ public partial class AudioPlayerProvider : ComponentBase, IAsyncDisposable
         _queueService.Attach(_audioPlayerService);
     }
 
+    /// <summary>
+    /// Warm the anon-id cache once the provider is interactive (Phase 16 wave 16.3). Done here, after the
+    /// first render, because the localStorage read is JS interop — not available during prerender. By the
+    /// time any play session closes and the sink reads <c>AnonId.Current</c>, the cache is populated; a
+    /// play that somehow closes before this completes simply sends no anonId (acceptable over-count). The
+    /// provider is the natural warm point: it is mounted in MainLayout, so it goes interactive on every
+    /// page the player can play from.
+    /// </summary>
+    protected override async Task OnAfterRenderAsync(bool firstRender)
+    {
+        if (firstRender)
+            await AnonId.EnsureLoadedAsync();
+    }
+
     /// <summary>
     /// Dispose the player on unmount so the JS setInterval driving progress
     /// callbacks no longer holds a DotNetObjectReference into a destroyed