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/auth/admin.guard.ts

@@ -0,0 +1,18 @@
+import { Injectable, CanActivate, ExecutionContext } from '@nestjs/common';
+import { UserRole } from '../user/user-role.enum';
+
+@Injectable()
+export class AdminGuard implements CanActivate {
+  canActivate(context: ExecutionContext): boolean {
+    const request = context.switchToHttp().getRequest();
+    const user = request.user;
+
+    // Check if user exists and has admin privileges (Super Admin or Tenant Admin)
+    return !!(
+      user &&
+      (user.role === UserRole.SUPER_ADMIN ||
+        user.role === UserRole.TENANT_ADMIN ||
+        user.isAdmin === true)
+    );
+  }
+}