feat: 文件存储安全加固 + 认证增强 + 媒体URL保护 + provider 重构

## 后端安全加固
- 新增 UserUploadPathResolver: 用户上传文件路径安全解析, 防目录穿越
- LocalReportFileStorage: 文件存储路径安全加固
- local_account_file_cleanup: 账号删除时文件清理逻辑增强
- AuthService: 认证逻辑增强
- file_endpoints / report_endpoints: 文件访问接口安全加固
- ai_chat_endpoints / doctor_endpoints: 接口安全调整
- Program.cs: 服务注册调整

## 前端认证与媒体
- 新增 authenticated_network_image.dart: 带认证的图片加载组件
- auth_provider: 认证状态管理大幅增强(+173)
- api_client: 网络客户端增强(+124)
- chat_provider: 聊天 provider 重构(+76)
- omron_device_provider: 蓝牙设备 provider 增强(+53)
- sse_handler: SSE 处理增强(+35)
- consultation_provider / data_providers / conversation_history_provider: 调整

## 页面调整
- remaining_pages: 健康档案/饮食记录等页面增强(+115)
- home_page / chat_messages_view: 主页微调
- doctor 端多页微调(consultations/dashboard/followups/patient_detail/profile/report_detail/reports)
- report_pages / settings_pages / notification_prefs_page: 微调
- device_scan_page / diet_capture_page / admin_home_page: 微调

## 测试
- 新增 file_path_security_tests: 文件路径安全测试
- 新增 protected_media_url_test: 媒体URL保护测试
- 新增 user_session_identity_test: 用户会话身份测试
- account_deletion_tests / application_service_tests / auth_tests: 更新

health_app/lib/providers/chat_provider.dart

@@ -86,10 +86,12 @@ class ChatNotifier extends Notifier<ChatState> {
   ActiveAgent? _lastTriggeredAgent;
   Timer? _agentTapLockTimer;
   bool _loadingConversation = false;
+  int _generation = 0;
 
   /// 重置整个会话：取消正在进行的 SSE，清空消息和会话 ID。
   /// 历史记录页一键清空 / 删除当前会话时调用。
   Future<void> resetSession() async {
+    _generation++;
     await _cancelActiveStream();
     _cancelPendingAgentWelcome();
     _lastTriggeredAgent = null;
@@ -140,7 +142,9 @@ class ChatNotifier extends Notifier<ChatState> {
 
   @override
   ChatState build() {
+    ref.watch(userSessionIdentityProvider);
     ref.onDispose(() {
+      _generation++;
       _subscription?.cancel();
       _agentTapLockTimer?.cancel();
       _subscription = null;
@@ -172,10 +176,13 @@ class ChatNotifier extends Notifier<ChatState> {
   }
 
   Future<String?> loadConversation(String convId) async {
-    if (state.isStreaming) return '小脉正在回复，请稍后再切换对话';
     if (_loadingConversation) return '正在加载其他对话，请稍候';
     _loadingConversation = true;
-    await _cancelActiveStream();
+    if (state.isStreaming) {
+      await stopGenerating();
+    } else {
+      await _cancelActiveStream();
+    }
     _cancelPendingAgentWelcome();
     try {
       final api = ref.read(apiClientProvider);
@@ -194,7 +201,9 @@ class ChatNotifier extends Notifier<ChatState> {
           role: role,
           content: map['content']?.toString() ?? '',
           createdAt:
-              DateTime.tryParse(map['createdAt']?.toString() ?? '') ??
+              DateTime.tryParse(
+                map['createdAt']?.toString() ?? '',
+              )?.toLocal() ??
               DateTime.now(),
           type: _messageTypeFromMetadata(metadata),
           metadata: metadata,
@@ -258,7 +267,8 @@ class ChatNotifier extends Notifier<ChatState> {
   Future<void> sendImage(String imagePath, String text) async {
     if (state.isStreaming) return;
     final file = File(imagePath);
-    if (!await file.exists()) return;
+    if (!await file.exists() || state.isStreaming) return;
+    final generation = ++_generation;
     _lastTriggeredAgent = null;
     _cancelPendingAgentWelcome();
     _resumeConversationFromHistory();
@@ -286,6 +296,8 @@ class ChatNotifier extends Notifier<ChatState> {
       uploadError = e;
     }
 
+    if (generation != _generation || !state.isStreaming) return;
+
     // 更新消息元数据（保留本地路径 + 添加远程URL）
     final updatedMsgs = state.messages.toList();
     final idx = updatedMsgs.indexWhere((m) => m.id == userMsg.id);
@@ -318,14 +330,15 @@ class ChatNotifier extends Notifier<ChatState> {
 
     // 把图片 URL 透传给后端，后端会调 VLM 识图并把描述拼到 LLM 上下文
     final userText = text.isNotEmpty ? text : '请帮我看看这张图片';
-    await _sendToAI(userText, imageUrl: uploadedUrl);
+    await _sendToAI(generation, userText, imageUrl: uploadedUrl);
   }
 
   /// 发送 PDF 附件 + 文字（PDF 解析在后端做）。
   Future<void> sendPdf(String pdfPath, String fileName, String text) async {
     if (state.isStreaming) return;
     final file = File(pdfPath);
-    if (!await file.exists()) return;
+    if (!await file.exists() || state.isStreaming) return;
+    final generation = ++_generation;
     _lastTriggeredAgent = null;
     _cancelPendingAgentWelcome();
     _resumeConversationFromHistory();
@@ -350,6 +363,8 @@ class ChatNotifier extends Notifier<ChatState> {
       // ignore，下方统一处理
     }
 
+    if (generation != _generation || !state.isStreaming) return;
+
     // 更新消息附带的远程 URL
     if (uploadedUrl != null) {
       final updatedMsgs = state.messages.toList();
@@ -376,11 +391,12 @@ class ChatNotifier extends Notifier<ChatState> {
       return;
     }
 
-    await _sendToAI(userMsg.content, pdfUrl: uploadedUrl);
+    await _sendToAI(generation, userMsg.content, pdfUrl: uploadedUrl);
   }
 
   Future<void> sendMessage(String text) async {
     if (text.trim().isEmpty || state.isStreaming) return;
+    final generation = ++_generation;
     _lastTriggeredAgent = null;
     _cancelPendingAgentWelcome();
     _resumeConversationFromHistory();
@@ -396,14 +412,16 @@ class ChatNotifier extends Notifier<ChatState> {
       isStreaming: true,
     );
 
-    await _sendToAI(text);
+    await _sendToAI(generation, text);
   }
 
   Future<void> _sendToAI(
+    int generation,
     String text, {
     String? imageUrl,
     String? pdfUrl,
   }) async {
+    if (generation != _generation || !state.isStreaming) return;
     final aiMsg = ChatMessage(
       id: '${DateTime.now().millisecondsSinceEpoch}_ai',
       role: 'assistant',
@@ -423,6 +441,7 @@ class ChatNotifier extends Notifier<ChatState> {
         _addError(aiMsg, '未登录，请重新登录');
         return;
       }
+      if (generation != _generation || !state.isStreaming) return;
 
       // 始终用 unified 智能体，AI 自动判断意图分配工具
       final stream = SseHandler.connect(
@@ -435,12 +454,18 @@ class ChatNotifier extends Notifier<ChatState> {
       );
 
       await _cancelActiveStream();
+      if (generation != _generation || !state.isStreaming) return;
+
       final done = Completer<void>();
       _streamDone = done;
       _subscription = stream.listen(
-        (event) => _processEvent(event, aiMsg),
+        (event) {
+          if (generation == _generation) _processEvent(event, aiMsg);
+        },
         onError: (_) {
-          _addError(aiMsg, '网络异常，请稍后重试');
+          if (generation == _generation) {
+            _addError(aiMsg, '网络异常，请稍后重试');
+          }
           if (!done.isCompleted) done.complete();
         },
         onDone: () {
@@ -454,11 +479,13 @@ class ChatNotifier extends Notifier<ChatState> {
         _subscription = null;
       }
 
-      if (state.isStreaming) {
+      if (generation == _generation && state.isStreaming) {
         _done(aiMsg);
       }
     } catch (e) {
-      _addError(aiMsg, '网络异常，请稍后重试');
+      if (generation == _generation) {
+        _addError(aiMsg, '网络异常，请稍后重试');
+      }
     }
   }
 
@@ -476,6 +503,31 @@ class ChatNotifier extends Notifier<ChatState> {
     _streamDone = null;
   }
 
+  Future<void> stopGenerating() async {
+    if (!state.isStreaming) return;
+    _generation++;
+    await _cancelActiveStream();
+    final messages = state.messages.toList();
+    if (messages.isNotEmpty &&
+        !messages.last.isUser &&
+        messages.last.type == MessageType.text) {
+      final last = messages.last;
+      if (last.content.trim().isEmpty) {
+        messages.removeLast();
+      } else {
+        last.content = '${last.content.trimRight()}\n\n（已停止生成）';
+        last.metadata = {...?last.metadata, 'generationStopped': true};
+        messages[messages.length - 1] = last;
+      }
+    }
+    state = state.copyWith(
+      messages: messages,
+      isStreaming: false,
+      thinkingText: null,
+    );
+    ref.invalidate(conversationHistoryProvider);
+  }
+
   void _addError(ChatMessage aiMsg, String errorText) {
     aiMsg.content = errorText;
     aiMsg.type = MessageType.text;