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/i18n/i18n.middleware.ts

@@ -0,0 +1,14 @@
+import { Injectable, NestMiddleware } from '@nestjs/common';
+import { Request, Response, NextFunction } from 'express';
+import { i18nStore } from './i18n.store';
+import { DEFAULT_LANGUAGE } from '../common/constants';
+
+@Injectable()
+export class I18nMiddleware implements NestMiddleware {
+  use(req: Request, res: Response, next: NextFunction) {
+    const language = req.headers['x-user-language'] || DEFAULT_LANGUAGE;
+    i18nStore.run({ language: String(language) }, () => {
+      next();
+    });
+  }
+}