feat: app 端 ui 设计完成

wei_ai_app/lib/models/message.dart

@@ -0,0 +1,22 @@
+enum MessageType { text, image, audio }
+enum MessageSender { user, ai }
+
+class Message {
+  final String id;
+  final String text;
+  final MessageSender sender;
+  final MessageType type;
+  final DateTime timestamp;
+  final String? imageUrl;
+  final bool isLocked;
+
+  const Message({
+    required this.id,
+    required this.text,
+    required this.sender,
+    required this.type,
+    required this.timestamp,
+    this.imageUrl,
+    this.isLocked = false,
+  });
+}