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/assessment/dto/update-template.dto.ts

@@ -0,0 +1,4 @@
+import { PartialType } from '@nestjs/mapped-types';
+import { CreateTemplateDto } from './create-template.dto';
+
+export class UpdateTemplateDto extends PartialType(CreateTemplateDto) {}