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/user/user-setting.service.ts

@@ -0,0 +1,29 @@
+import { Injectable } from '@nestjs/common';
+import { InjectRepository } from '@nestjs/typeorm';
+import { Repository } from 'typeorm';
+import { UserSetting } from './user-setting.entity';
+
+@Injectable()
+export class UserSettingService {
+  constructor(
+    @InjectRepository(UserSetting)
+    private userSettingRepository: Repository<UserSetting>,
+  ) {}
+
+  async getByUser(userId: string): Promise<UserSetting> {
+    let setting = await this.userSettingRepository.findOne({
+      where: { userId },
+    });
+    if (!setting) {
+      setting = this.userSettingRepository.create({ userId, language: 'zh' });
+      await this.userSettingRepository.save(setting);
+    }
+    return setting;
+  }
+
+  async update(userId: string, language: string): Promise<UserSetting> {
+    const setting = await this.getByUser(userId);
+    setting.language = language;
+    return this.userSettingRepository.save(setting);
+  }
+}