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/common/common.module.ts

@@ -0,0 +1,11 @@
+import { Module } from '@nestjs/common';
+import { CampusScope } from './campus-scope';
+import { CampusScopeMiddleware } from './campus-scope.middleware';
+import { DepartmentsModule } from '../departments/departments.module';
+
+@Module({
+  imports: [DepartmentsModule],
+  providers: [CampusScope, CampusScopeMiddleware],
+  exports: [CampusScope, CampusScopeMiddleware, DepartmentsModule],
+})
+export class CommonModule {}