feat: implement QuestionBank CRUD with pagination and template query

- Add pagination support to findAll (page, limit query params)
- Add findByTemplateId method to service
- Add GET /by-template/:templateId endpoint to controller
- Service already includes CRUD for QuestionBank and QuestionBankItem

server/src/admin/admin.module.ts

@@ -0,0 +1,12 @@
+import { Module } from '@nestjs/common';
+import { AdminController } from './admin.controller';
+import { AdminService } from './admin.service';
+import { UserModule } from '../user/user.module';
+import { TenantModule } from '../tenant/tenant.module';
+
+@Module({
+  imports: [UserModule, TenantModule],
+  controllers: [AdminController],
+  providers: [AdminService],
+})
+export class AdminModule {}