Fix CmsKit media download

modules/cms-kit/src/Volo.CmsKit.Common.Application/Volo/CmsKit/MediaDescriptors/MediaDescriptorAppService.cs

@@ -24,6 +24,11 @@ namespace Volo.CmsKit.MediaDescriptors
             var entity = await MediaDescriptorRepository.GetAsync(id);
             var stream = await MediaContainer.GetAsync(id.ToString());
 
+            if (stream.CanSeek)
+            {
+                stream.Position = 0;
+            }
+
             return new RemoteStreamContent(stream, entity.Name, entity.MimeType);
         }
     }