fix editing non-timed annotations

Azaion.Annotator/DTO/ThumbnailDto.cs

@@ -1,4 +1,5 @@
 using System.ComponentModel;
+using System.IO;
 using System.Runtime.CompilerServices;
 using System.Windows.Media.Imaging;
 using Azaion.Annotator.Extensions;
@@ -26,6 +27,7 @@ public class ThumbnailDto : INotifyPropertyChanged
             OnPropertyChanged();
         }
     }
+    public string ImageName => Path.GetFileName(ImagePath);
 
     public void UpdateImage() => _image = null;