新增AI教练模块，包括控制器、服务、模型及数据传输对象，更新应用模块以引入新模块，同时在打卡模块中添加按时间范围返回每日打卡状态的功能

src/ai-coach/models/ai-message.model.ts

@@ -0,0 +1,62 @@
+import { Column, DataType, Index, Model, PrimaryKey, Table } from 'sequelize-typescript';
+
+export enum RoleType {
+  System = 'system',
+  User = 'user',
+  Assistant = 'assistant',
+}
+
+@Table({
+  tableName: 't_ai_messages',
+  underscored: true,
+})
+export class AiMessage extends Model {
+  @PrimaryKey
+  @Column({
+    type: DataType.STRING,
+    allowNull: false,
+    comment: '会话ID',
+    primaryKey: true,
+  })
+  declare conversationId: string;
+
+  @Column({
+    type: DataType.STRING,
+    allowNull: false,
+    comment: '用户ID',
+  })
+  declare userId: string;
+
+  @Column({
+    type: DataType.ENUM('system', 'user', 'assistant'),
+    allowNull: false,
+  })
+  declare role: RoleType;
+
+  @Column({
+    type: DataType.TEXT('long'),
+    allowNull: false,
+  })
+  declare content: string;
+
+  @Column({
+    type: DataType.JSON,
+    allowNull: true,
+    comment: '扩展元数据，如token用量、模型名等',
+  })
+  declare metadata: Record<string, any> | null;
+
+  @Column({
+    type: DataType.DATE,
+    defaultValue: DataType.NOW,
+  })
+  declare createdAt: Date;
+
+  @Column({
+    type: DataType.DATE,
+    defaultValue: DataType.NOW,
+  })
+  declare updatedAt: Date;
+}
+
+