fix: 数据确认面板修复 - 显示实际数值+确认关闭+侧边栏刷新+清理旧数据

- Handler返回value/unit/isAbnormal到metadata
- DataConfirmCard显示实际数值和单位
- 确认按钮关闭卡片+刷新健康概览
- 健康Agent欢迎卡简化为'查看趋势'
- 清空87条旧健康测试数据

health_app/lib/providers/chat_provider.dart

@@ -14,6 +14,7 @@ class ChatMessage {
   final DateTime createdAt;
   MessageType type;
   final Map<String, dynamic>? metadata;
+  bool confirmed;
   ChatMessage({
     required this.id,
     required this.role,
@@ -21,6 +22,7 @@ class ChatMessage {
     required this.createdAt,
     this.type = MessageType.text,
     this.metadata,
+    this.confirmed = false,
   });
   bool get isUser => role == 'user';
 }
@@ -114,6 +116,8 @@ ActiveAgent _parseAgent(String? type) {
 class ChatNotifier extends Notifier<ChatState> {
   StreamSubscription<Map<String, dynamic>>? _subscription;
 
+  void markNeedsRebuild() => state = state.copyWith();
+
   @override
   ChatState build() {
     Future.microtask(() {