feat: 集成 AI 对话与只读查询工具

apps/server/src/ai-chat/entities/ai-message.entity.ts

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+import {
+  Column,
+  CreateDateColumn,
+  Entity,
+  Index,
+  JoinColumn,
+  ManyToOne,
+  OneToMany,
+  PrimaryGeneratedColumn,
+  UpdateDateColumn,
+} from 'typeorm';
+import { AiConversation } from './ai-conversation.entity';
+import { AiToolRun } from './ai-tool-run.entity';
+
+export type AiMessageRole = 'user' | 'assistant';
+export type AiMessageStatus = 'pending' | 'completed' | 'failed' | 'cancelled';
+
+@Entity('ai_messages')
+@Index('idx_ai_messages_conversation_created', ['conversationId', 'createdAt'])
+export class AiMessage {
+  @PrimaryGeneratedColumn()
+  id: number;
+
+  @Column({ name: 'conversation_id', type: 'integer' })
+  conversationId: number;
+
+  @ManyToOne(() => AiConversation, (conversation) => conversation.messages, {
+    onDelete: 'CASCADE',
+  })
+  @JoinColumn({ name: 'conversation_id' })
+  conversation: AiConversation;
+
+  @Column({ type: 'varchar', length: 20 })
+  role: AiMessageRole;
+
+  @Column({ type: 'text', default: '' })
+  content: string;
+
+  @Column({ name: 'reasoning_content', type: 'text', nullable: true })
+  reasoningContent: string | null;
+
+  @Column({ type: 'varchar', length: 20, default: 'completed' })
+  status: AiMessageStatus;
+
+  @Column({ name: 'error_code', type: 'varchar', length: 50, nullable: true })
+  errorCode: string | null;
+
+  @OneToMany(() => AiToolRun, (run) => run.message)
+  toolRuns: AiToolRun[];
+
+  @CreateDateColumn({ name: 'created_at', type: 'datetime' })
+  createdAt: Date;
+
+  @UpdateDateColumn({ name: 'updated_at', type: 'datetime' })
+  updatedAt: Date;
+}