feat(phase-16): anonymous play & share telemetry substrate (wave 16.1)

Player-service play-session tracker (floor + 3-bucket classify), SharePopover share tracker with debounce, sendBeacon interop, proxied rate-limited POST api/event/{play,share}, append-only event logs + incremental play_counter with server-side release resolution. Migration authored, not applied. No anonId, no read surface.

DeepDrftPublic.Client/Controls/SharePopover.razor.cs

@@ -1,5 +1,6 @@
 using DeepDrftModels.Enums;
 using DeepDrftPublic.Client.Common;
+using DeepDrftPublic.Client.Services;
 using Microsoft.AspNetCore.Components;
 using Microsoft.JSInterop;
 
@@ -27,6 +28,7 @@ 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; }
 
     private bool IsReleaseMode => ReleaseEntryKey is not null;
 
@@ -67,6 +69,14 @@ public partial class SharePopover : ComponentBase, IDisposable
     {
         if (await CopyToClipboard(LinkUrl))
         {
+            // Record a share only after the clipboard write succeeds (§1b). Release mode targets the
+            // release EntryKey; track mode targets the track EntryKey. The tracker debounces repeat
+            // copies of the same (target, channel) into one event.
+            if (IsReleaseMode)
+                ShareTracker.RecordShare(ShareTargetType.Release, ReleaseEntryKey!, ShareChannel.Link);
+            else if (!string.IsNullOrWhiteSpace(EntryKey))
+                ShareTracker.RecordShare(ShareTargetType.Track, EntryKey, ShareChannel.Link);
+
             _linkCopied = true;
             await ResetAfterDelay(() => _linkCopied = false);
         }
@@ -76,6 +86,11 @@ public partial class SharePopover : ComponentBase, IDisposable
     {
         if (await CopyToClipboard(EmbedSnippet))
         {
+            // Embed is a single-track affordance only (release mode hides it), so this always targets a
+            // track with channel = embed.
+            if (!string.IsNullOrWhiteSpace(EntryKey))
+                ShareTracker.RecordShare(ShareTargetType.Track, EntryKey, ShareChannel.Embed);
+
             _embedCopied = true;
             await ResetAfterDelay(() => _embedCopied = false);
         }