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/pages/home/home_page.dart

@@ -85,6 +85,7 @@ class _HomePageState extends ConsumerState<HomePage>
   }
 
   void _sendMessage() {
+    if (ref.read(chatProvider).isStreaming) return;
     final text = _textCtrl.text.trim();
     final imagePath = _pickedImagePath;
     if (text.isEmpty && imagePath == null) return;
@@ -425,6 +426,9 @@ class _HomePageState extends ConsumerState<HomePage>
   }
 
   Widget _buildInputBar() {
+    final isStreaming = ref.watch(
+      chatProvider.select((state) => state.isStreaming),
+    );
     return Padding(
       padding: const EdgeInsets.fromLTRB(12, 0, 12, 10),
       child: Container(
@@ -490,7 +494,9 @@ class _HomePageState extends ConsumerState<HomePage>
               color: Colors.transparent,
               child: InkWell(
                 customBorder: const CircleBorder(),
-                onTap: _sendMessage,
+                onTap: isStreaming
+                    ? () => ref.read(chatProvider.notifier).stopGenerating()
+                    : _sendMessage,
                 child: Ink(
                   width: 38,
                   height: 38,
@@ -498,8 +504,8 @@ class _HomePageState extends ConsumerState<HomePage>
                     gradient: AppColors.primaryGradient,
                     shape: BoxShape.circle,
                   ),
-                  child: const Icon(
-                    LucideIcons.send,
+                  child: Icon(
+                    isStreaming ? Icons.stop_rounded : LucideIcons.send,
                     size: 18,
                     color: Colors.white,
                   ),