refactor(server): remove Department/UserDepartment entities, CampusScope, and departmentId from all entities

- Delete department.entity.ts, user-department.entity.ts
- Remove Department/UserDepartment from entities/index.ts
- Remove departmentId column from 18 entities (AttendanceRecord, ArchiveAttachment, Bill, ClassSchedule, Classroom, ClassroomRental, Deposit, DepositInstallment, ExamScore, LearningRecord, Occupancy, PersonalExpense, ResultArchive, Room, RoomExpense, Student, StudentEnrollment, StudentProfile, StudentReport)
- Remove departments/ module entirely
- Delete campus-scope.ts, campus-scope.middleware.ts (request-utils.ts kept — it's just IP extraction)
- Simplify common.module.ts to empty module
- Remove CampusScopeMiddleware from app.module.ts
- Remove all CampusScope injections and filter calls across all services
- Remove departmentId from all DTOs and controllers
- Simplify dingtalk/wecom sync to only sync users (no dept table)
- Update seed module to remove department seeding
- Clean frontend compilation

apps/server/src/classes/classes.service.ts

@@ -147,7 +147,6 @@ export class ClassesService {
         this.studentRepo.create({
           name: `dd_${dingUserId}`,
           status: 'active',
-          departmentId: undefined,
         })
       );
       const savedStudents = await this.studentRepo.save(newStudents);