feat(ov): windowed dedup visit counting with retention cleanup

Task 8 (P2): POST /public/albums/{token}/visits with visit_sessions
window dedup (VISIT_WINDOW_MINUTES), requestId idempotent replay
(echoes stored outcome; expired beyond VISIT_REQUEST_TTL_MINUTES
rejected), album_stats viewCount/statVersion authority + outbox_stat_events
views snapshots, WS stats.updated broadcast, visitorId+IP fixed-window
rate limit (VISIT_WINDOW_REQUESTS), and ov CleanupModule scheduler
(setInterval, CLEANUP_INTERVAL_MINUTES) deleting like_batches /
visit_requests / visit_sessions past their windows — totals never
touched. Contract prose aligned to replay semantics; constants
VISIT_WINDOW_REQUESTS / CLEANUP_INTERVAL_MINUTES added.

Co-Authored-By: Claude Code <noreply@anthropic.com>

services/api/src/realtime/realtime.gateway.ts

@@ -44,8 +44,10 @@ import { isAlbumVisibleOv } from '../shared/album-visibility';
 import {
   OV_LIKE_BATCH_COMMITTED,
   OV_PHOTO_APPLIED,
+  OV_VISIT_COUNTED,
   type LikeBatchCommittedEvent,
   type PhotoAppliedEvent,
+  type VisitCountedEvent,
 } from './ov-events';
 
 /** likes.burst 合并窗口毫秒（惰性读 env，0=逐批即时广播；e2e 可调）。 */
@@ -227,6 +229,17 @@ export class RealtimeGateway implements OnModuleDestroy {
     pending.originBatchIds.push(event.batchId);
   }
 
+  /** 浏览已计入 → 原样转发契约 stats.updated 消息到相册房间（Task 8）。 */
+  @OnEvent(OV_VISIT_COUNTED)
+  onVisitCounted(event: VisitCountedEvent): void {
+    this.sendToRoom(event.albumId, {
+      type: 'stats.updated',
+      albumId: event.albumId,
+      viewCount: event.viewCount,
+      countVersion: event.statVersion,
+    });
+  }
+
   /** 副本照片可见性应用 → 原样转发契约 photo.* 消息到相册房间。 */
   @OnEvent(OV_PHOTO_APPLIED)
   onPhotoApplied(event: PhotoAppliedEvent): void {