refactor(data/models): 重构消息模型以支持更多功能

- 将`role`字段改为更明确的`isUser`布尔值
- 重命名`content`为`text`以提高可读性
- 添加`hasImage`和`imagePath`支持图片消息
- 新增`meta`字段用于存储卡片数据
- 将`isLoading`改为`isRecognizing`以更准确描述语音识别状态

lib/data/models/message_model.dart

@@ -1,58 +1,77 @@
 class Message {
-  final String role; // 'user' or 'assistant'
-  final String content;
-  final DateTime timestamp;
-  final bool isLoading;
+  final bool isUser; //标识信息是否来自用户还是AI
+  final String text; //信息文本内容
+  final DateTime timestamp; // 消息时间戳
+  final bool isRecognizing; // 是否为语音识别中的临时消息
+  final bool hasImage; // 是否包含图片
+  final String? imagePath; // 图片路径
+  final Map? meta; //卡片数据
 
   Message({
-    required this.role,
-    required this.content,
-    required this.timestamp,
-    this.isLoading = false,
-  });
+    // 构造函数
+    required this.isUser,
+    required this.text,
+    DateTime? timestamp,
+    this.isRecognizing = false,
+    this.hasImage = false,
+    this.imagePath,
+    this.meta,
+  }) : this.timestamp = timestamp ?? DateTime.now();
 
   // 从JSON构造函数
   factory Message.fromJson(Map<String, dynamic> json) {
     return Message(
-      role: json['role'] as String,
-      content: json['content'] as String,
+      isUser: json['isUser'] as bool,
+      text: json['text'] as String,
       timestamp: DateTime.parse(json['timestamp'] as String),
-      isLoading: json['isLoading'] as bool? ?? false,
+      isRecognizing: json['isRecognizing'] as bool? ?? false,
+      hasImage: json['hasImage'] as bool? ?? false,
+      imagePath: json['imagePath'] as String?,
+      meta: json['meta'] as Map?,
     );
   }
 
   // 转换为JSON
   Map<String, dynamic> toJson() {
     return {
-      'role': role,
-      'content': content,
+      'isUser': isUser,
+      'text': text,
       'timestamp': timestamp.toIso8601String(),
-      'isLoading': isLoading,
+      'isRecognizing': isRecognizing,
+      'hasImage': hasImage,
+      'imagePath': imagePath,
+      'meta': meta,
     };
   }
 
   // 创建一个加载中的消息
   factory Message.loading() {
     return Message(
-      role: 'assistant',
-      content: '',
+      isUser: false,
+      text: '',
       timestamp: DateTime.now(),
-      isLoading: true,
+      isRecognizing: true,
     );
   }
 
   // 复制并修改
   Message copyWith({
-    String? role,
-    String? content,
+    bool? isUser,
+    String? text,
     DateTime? timestamp,
-    bool? isLoading,
+    bool? isRecognizing,
+    bool? hasImage,
+    String? imagePath,
+    Map? meta,
   }) {
     return Message(
-      role: role ?? this.role,
-      content: content ?? this.content,
+      isUser: isUser ?? this.isUser,
+      text: text ?? this.text,
       timestamp: timestamp ?? this.timestamp,
-      isLoading: isLoading ?? this.isLoading,
+      isRecognizing: isRecognizing ?? this.isRecognizing,
+      hasImage: hasImage ?? this.hasImage,
+      imagePath: imagePath ?? this.imagePath,
+      meta: meta ?? this.meta,
     );
   }
 }