feat: P2-15 cron-based DingTalk/WeCom sync with logging and incremental sync

- Add @nestjs/schedule dependency
- Create SyncLog entity (platform, syncType, status, recordsCount, errorMessage, timestamps)
- Create SyncState entity for tracking lastSyncAt per platform
- SyncService with @Cron('0 2 * * *') daily scheduled sync
- Incremental sync: tracks last_sync_at per platform, passes to integration APIs
- Full/incremental mode determined by existence of prior sync
- SyncController: POST /sync/trigger (manual), GET /sync/logs (history)
- Register SyncModule in AppModule with ScheduleModule

apps/server/src/sync/sync.controller.ts

@@ -0,0 +1,27 @@
+import { Controller, Get, Post, Query, UseGuards } from '@nestjs/common';
+import { JwtAuthGuard } from '../auth/guards/jwt-auth.guard';
+import { RequirePermission } from '../auth/decorators/permission.decorator';
+import { SyncService } from './sync.service';
+import type { SyncPlatform } from '../entities/sync-log.entity';
+
+@UseGuards(JwtAuthGuard)
+@Controller('sync')
+export class SyncController {
+  constructor(private readonly syncService: SyncService) {}
+
+  @Post('trigger')
+  @RequirePermission('sync:trigger')
+  async triggerSync(@Query('platform') platform?: SyncPlatform) {
+    const logs = await this.syncService.triggerSync(platform);
+    return { synced: logs.length, logs };
+  }
+
+  @Get('logs')
+  @RequirePermission('sync:read')
+  async getLogs(
+    @Query('platform') platform?: SyncPlatform,
+    @Query('limit') limit?: number,
+  ) {
+    return this.syncService.getLogs(platform, limit ? Number(limit) : 50);
+  }
+}