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/knowledge-base/dto/create-knowledge-base.dto.ts

@@ -0,0 +1,11 @@
+import { IsNotEmpty, IsOptional, IsString } from 'class-validator';
+
+export class CreateKnowledgeBaseDto {
+  @IsString()
+  @IsNotEmpty()
+  name: string;
+
+  @IsString()
+  @IsOptional()
+  description?: string;
+}