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/search-history/chat-message.entity.ts

@@ -0,0 +1,44 @@
+import {
+  Entity,
+  PrimaryGeneratedColumn,
+  Column,
+  CreateDateColumn,
+  ManyToOne,
+  JoinColumn,
+} from 'typeorm';
+import { SearchHistory } from './search-history.entity';
+import { Tenant } from '../tenant/tenant.entity';
+
+@Entity('chat_messages')
+export class ChatMessage {
+  @PrimaryGeneratedColumn('uuid')
+  id: string;
+
+  @Column({ name: 'search_history_id' })
+  searchHistoryId: string;
+
+  @Column({ name: 'tenant_id', nullable: true, type: 'text' })
+  tenantId: string;
+
+  @Column()
+  role: 'user' | 'assistant';
+
+  @Column('text')
+  content: string;
+
+  @Column({ nullable: true })
+  sources?: string; // JSON string
+
+  @CreateDateColumn({ name: 'created_at' })
+  createdAt: Date;
+
+  @ManyToOne(() => SearchHistory, (history) => history.messages, {
+    onDelete: 'CASCADE',
+  })
+  @JoinColumn({ name: 'search_history_id' })
+  searchHistory: SearchHistory;
+
+  @ManyToOne(() => Tenant)
+  @JoinColumn({ name: 'tenant_id' })
+  tenant: Tenant;
+}