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/consultation_provider.dart

@@ -89,7 +89,14 @@ class ConsultationChatNotifier extends Notifier<ConsultationChatState> {
   String get _hubUrl => '$baseUrl/hubs/consultation';
 
   @override
-  ConsultationChatState build() => const ConsultationChatState();
+  ConsultationChatState build() {
+    ref.watch(userSessionIdentityProvider);
+    ref.onDispose(() async {
+      await _hub?.stop();
+      _hub = null;
+    });
+    return const ConsultationChatState();
+  }
 
   Future<void> init(String doctorId) async {
     state = state.copyWith(doctorId: doctorId, isLoading: true);
@@ -169,7 +176,7 @@ class ConsultationChatNotifier extends Notifier<ConsultationChatState> {
           senderName: data['senderName']?.toString(),
           content: data['content']?.toString() ?? '',
           createdAt: data['createdAt'] != null
-              ? DateTime.tryParse(data['createdAt'].toString()) ??
+              ? DateTime.tryParse(data['createdAt'].toString())?.toLocal() ??
                     DateTime.now()
               : DateTime.now(),
         );
@@ -228,7 +235,9 @@ class ConsultationChatNotifier extends Notifier<ConsultationChatState> {
           senderName: map['senderName']?.toString(),
           content: map['content']?.toString() ?? '',
           createdAt:
-              DateTime.tryParse(map['createdAt']?.toString() ?? '') ??
+              DateTime.tryParse(
+                map['createdAt']?.toString() ?? '',
+              )?.toLocal() ??
               DateTime.now(),
         );
       }).toList();
@@ -354,7 +363,9 @@ class ConsultationChatNotifier extends Notifier<ConsultationChatState> {
               senderName: map['senderName']?.toString(),
               content: map['content']?.toString() ?? '',
               createdAt:
-                  DateTime.tryParse(map['createdAt']?.toString() ?? '') ??
+                  DateTime.tryParse(
+                    map['createdAt']?.toString() ?? '',
+                  )?.toLocal() ??
                   DateTime.now(),
             );
           })