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

docker-compose.yml

@@ -17,7 +17,9 @@ services:
     command: --default-authentication-plugin=mysql_native_password --character-set-server=utf8mb4 --collation-server=utf8mb4_unicode_ci
 
   backend:
-    build: ./apps/server
+    build:
+      context: .
+      dockerfile: apps/server/Dockerfile
     container_name: dorm_billing_backend
     restart: always
     ports:
@@ -34,7 +36,9 @@ services:
       - mysql
 
   frontend:
-    build: ./apps/admin
+    build:
+      context: .
+      dockerfile: apps/admin/Dockerfile
     container_name: dorm_billing_frontend
     restart: always
     ports: