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.

DeepDrftData/EventManager.cs

@@ -0,0 +1,56 @@
+using DeepDrftData.Repositories;
+using DeepDrftModels.Enums;
+using Microsoft.Extensions.Logging;
+using NetBlocks.Models;
+
+namespace DeepDrftData;
+
+/// <summary>
+/// <see cref="IEventService"/> implementation over <see cref="EventRepository"/>. The layer boundary
+/// matches the rest of DeepDrftData: the repository owns the EF constructs and the write transaction;
+/// this service catches at the boundary and returns a NetBlocks <see cref="Result"/>. Telemetry is
+/// best-effort by design (§2.2) — a failed write is logged and surfaced as a fail result, never thrown
+/// at the caller, so a telemetry hiccup can never reach a listener.
+/// </summary>
+public class EventManager : IEventService
+{
+    private readonly EventRepository _repository;
+    private readonly ILogger<EventManager> _logger;
+
+    public EventManager(EventRepository repository, ILogger<EventManager> logger)
+    {
+        _repository = repository;
+        _logger = logger;
+    }
+
+    public async Task<Result> RecordPlay(
+        string trackEntryKey, PlayBucket bucket, string? anonId = null, CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            await _repository.RecordPlayAsync(trackEntryKey, bucket, anonId, cancellationToken);
+            return Result.CreatePassResult();
+        }
+        catch (Exception e)
+        {
+            _logger.LogError(e, "Failed to record play event for track {TrackEntryKey}", trackEntryKey);
+            return Result.CreateFailResult(e.Message);
+        }
+    }
+
+    public async Task<Result> RecordShare(
+        ShareTargetType targetType, string targetKey, ShareChannel channel, string? anonId = null,
+        CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            await _repository.RecordShareAsync(targetType, targetKey, channel, anonId, cancellationToken);
+            return Result.CreatePassResult();
+        }
+        catch (Exception e)
+        {
+            _logger.LogError(e, "Failed to record share event for {TargetType} {TargetKey}", targetType, targetKey);
+            return Result.CreateFailResult(e.Message);
+        }
+    }
+}