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

backend/src/Health.WebApi/Endpoints/ai_chat_endpoints.cs

@@ -24,13 +24,12 @@ public static class AiChatEndpoints
 
     public static void MapAiChatEndpoints(this WebApplication app)
     {
-        // SSE 流式对话（GET 方式，token 通过 query string 传递）
+        // SSE 流式对话。认证统一走 ASP.NET Core JWT 中间件。
         app.MapGet("/api/ai/{agentType}/chat", async (
             string message,
             string? conversationId,
             string? imageUrl,
             string? pdfUrl,
-            string token,
             string agentType,
             HttpContext http,
             DeepSeekClient llmClient,
@@ -43,8 +42,7 @@ public static class AiChatEndpoints
             IPatientContextService patientContexts,
             CancellationToken ct) =>
         {
-            // 支持 token 通过 query string（浏览器 EventSource）或 header 传递
-            var userId = GetUserId(http) ?? GetUserIdFromToken(token);
+            var userId = GetUserId(http);
             if (userId == null)
             {
                 http.Response.StatusCode = 401;
@@ -89,7 +87,7 @@ public static class AiChatEndpoints
                 await SseWriteAsync(http, new { action = "conversation_id", data = activeConversationId.ToString() }, ct);
 
             // 附件解析（图片走 VLM、PDF 走 PdfPig），结果同时拼 LLM 上下文 + 持久化到 user message metadata
-            var attachment = await attachments.BuildAsync(imageUrl, pdfUrl, ct);
+            var attachment = await attachments.BuildAsync(userId.Value, imageUrl, pdfUrl, ct);
             string? userMessageMetadataJson = null;
             if (attachment != null)
             {
@@ -277,7 +275,7 @@ public static class AiChatEndpoints
 
             await SseWriteAsync(http, new { action = "status", data = completedNormally ? "done" : "error" }, ct);
             await http.Response.WriteAsync("data: [DONE]\n\n", ct);
-        });
+        }).RequireAuthorization();
 
         app.MapPost("/api/ai/confirm-write/{commandId:guid}", async (
             Guid commandId,
@@ -327,7 +325,7 @@ public static class AiChatEndpoints
                 : Results.Json(
                     new { code = 40401, data = (object?)null, message = "对话不存在" },
                     statusCode: StatusCodes.Status404NotFound);
-        });
+        }).RequireAuthorization();
 
         // 一键清空当前用户的全部对话
         app.MapDelete("/api/ai/conversations", async (HttpContext http, IAiConversationService conversations, CancellationToken ct) =>
@@ -421,19 +419,6 @@ public static class AiChatEndpoints
     private static Guid? GetUserId(HttpContext http) =>
         Guid.TryParse(http.User.FindFirst(System.Security.Claims.ClaimTypes.NameIdentifier)?.Value, out var id) ? id : null;
 
-    private static Guid? GetUserIdFromToken(string? token)
-    {
-        if (string.IsNullOrEmpty(token)) return null;
-        try
-        {
-            var handler = new System.IdentityModel.Tokens.Jwt.JwtSecurityTokenHandler();
-            var jwt = handler.ReadJwtToken(token);
-            var sub = jwt.Claims.FirstOrDefault(c => c.Type == System.Security.Claims.ClaimTypes.NameIdentifier)?.Value;
-            return sub != null && Guid.TryParse(sub, out var id) ? id : null;
-        }
-        catch (Exception) { return null; }
-    }
-
     private static async Task TryUpdateConversationSummaryAsync(
         IAiConversationService conversations,
         DeepSeekClient llmClient,