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/app.module.ts

@@ -25,6 +25,8 @@ import {
   ClassSchedule,
   AttendanceRecord,
   DingAttendanceRaw,
+  SyncLog,
+  SyncState,
 } from './entities';
 import { AuthModule } from './auth/auth.module';
 import { RbacModule } from './rbac/rbac.module';
@@ -43,6 +45,7 @@ import { TenantsModule } from './tenants/tenants.module';
 import { AttendanceModule } from './attendance/attendance.module';
 import { SchedulesModule } from './schedules/schedules.module';
 import { ClassroomRentalsModule } from './classroom-rentals/classroom-rentals.module';
+import { SyncModule } from './sync/sync.module';
 
 @Module({
   imports: [
@@ -77,6 +80,8 @@ import { ClassroomRentalsModule } from './classroom-rentals/classroom-rentals.mo
           ClassSchedule,
           AttendanceRecord,
           DingAttendanceRaw,
+          SyncLog,
+          SyncState,
         ];
         if (dbType === 'mysql') {
           return {
@@ -115,6 +120,7 @@ import { ClassroomRentalsModule } from './classroom-rentals/classroom-rentals.mo
     TenantsModule,
     SchedulesModule,
     ClassroomRentalsModule,
+    SyncModule,
   ],
   providers: [
     { provide: APP_GUARD, useClass: ThrottlerGuard },