feat(sync): cn event coverage, bootstrap and outbox sender

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

services/api/src/sync/sync.module.ts

@@ -0,0 +1,12 @@
+// services/api/src/sync/sync.module.ts —— cn 侧内部同步模块（P2 Task 3）。
+// bootstrap/reconcile 端点 + 载荷构建器（payloads.ts 供 albums/categories/
+// assets/photos 业务服务与快照生成共用）。PrismaService 经 @Global 注入。
+import { Module } from '@nestjs/common';
+import { SyncController } from './sync.controller';
+import { SyncService } from './sync.service';
+
+@Module({
+  controllers: [SyncController],
+  providers: [SyncService],
+})
+export class SyncModule {}