fix: 修复数据库与SignalR无法连接的问题

server/src/Controllers/VideoStreamController.cs

@@ -18,7 +18,7 @@ public class VideoStreamController : ControllerBase
     private static NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger();
 
     private readonly HttpVideoStreamService _videoStreamService;
-    private readonly Database.UserManager _userManager;
+    private readonly Database.UserManager _userManager = new();
 
     public class AvailableResolutionsResponse
     {
@@ -32,13 +32,10 @@ public class VideoStreamController : ControllerBase
     /// 初始化HTTP视频流控制器
     /// </summary>
     /// <param name="videoStreamService">HTTP视频流服务</param>
-    /// <param name="userManager">用户管理服务</param>
-    public VideoStreamController(
-        HttpVideoStreamService videoStreamService, Database.UserManager userManager)
+    public VideoStreamController(HttpVideoStreamService videoStreamService)
     {
         logger.Info("创建VideoStreamController，命名空间：{Namespace}", this.GetType().Namespace);
         _videoStreamService = videoStreamService;
-        _userManager = userManager;
     }
 
     private Optional<string> TryGetBoardId()