feat(rbac): add Permission and Role entities, update User entity

backend/src/entities/index.ts

@@ -11,3 +11,5 @@ export { Deposit } from './deposit.entity';
 export { Classroom } from './classroom.entity';
 export { Tenant } from './tenant.entity';
 export { ClassroomRental } from './classroom-rental.entity';
+export { Permission } from './permission.entity';
+export { Role } from './role.entity';