feat: complete PRD verification fixes and deployment readiness

- Add CommonModule to provide/export CampusScope across business modules
- Replace DepartmentsModule imports with CommonModule in 11 modules
- Add missing Class/Tenant repository imports to StudentsModule and SchedulesModule
- Fix service specs with CampusScope, ClassRepository, StudentRepository mocks
- Move better-sqlite3 to optionalDependencies for production Docker builds
- Rewrite Dockerfiles for monorepo root build context
- Update docker-compose.yml service build contexts

apps/server/src/bills/bills.module.ts

@@ -1,6 +1,6 @@
 import { Module } from '@nestjs/common';
 import { NotificationsModule } from '../notifications/notifications.module';
-import { DepartmentsModule } from '../departments/departments.module';
+import { CommonModule } from '../common/common.module';
 import { TypeOrmModule } from '@nestjs/typeorm';
 import { Bill } from '../entities/bill.entity';
 import { BillItem } from '../entities/bill-item.entity';
@@ -27,7 +27,7 @@ import { BillsController } from './bills.controller';
       Student,
     ]),
     NotificationsModule,
-    DepartmentsModule,
+    CommonModule,
   ],
   controllers: [BillsController],
   providers: [BillsService, BillsExportService],