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/SharePopover.razor.cs

@@ -30,6 +30,7 @@ public partial class SharePopover : ComponentBase, IDisposable
     [Inject] public required NavigationManager Navigation { get; set; }
     [Inject] public required IJSRuntime JS { get; set; }
     [Inject] public required ShareTracker ShareTracker { get; set; }
+    [Inject] public required IAnonIdProvider AnonId { get; set; }
 
     private bool IsReleaseMode => ReleaseEntryKey is not null;
 
@@ -65,7 +66,15 @@ public partial class SharePopover : ComponentBase, IDisposable
         ? EmbedSnippetBuilder.ForRelease(Navigation.BaseUri, ReleaseEntryKey!)
         : EmbedSnippetBuilder.ForTrack(Navigation.BaseUri, EntryKey!);
 
-    private void Toggle() => _open = !_open;
+    private async Task Toggle()
+    {
+        _open = !_open;
+        // Warm the anon-id cache when the popover opens (wave 16.3) so a copy-share fired moments later
+        // reads a populated AnonId.Current. Idempotent and best-effort — if it fails the share simply
+        // carries no anonId. Opening is interactive, so the localStorage interop is available here.
+        if (_open)
+            await AnonId.EnsureLoadedAsync();
+    }
 
     private void Close() => _open = false;