Backport pull request #12490 from jellyfin/release-10.9.z

Set Content-Disposition header to attachment for image endpoints

Original-merge: 9645955629

Merged-by: crobibero <cody@robibe.ro>

Backported-by: Joshua M. Boniface <joshua@boniface.me>

Jellyfin.Api/Controllers/TrickplayController.cs

@@ -95,6 +95,7 @@ public class TrickplayController : BaseJellyfinApiController
         var path = _trickplayManager.GetTrickplayTilePath(item, width, index);
         if (System.IO.File.Exists(path))
         {
+            Response.Headers.ContentDisposition = "attachment";
             return PhysicalFile(path, MediaTypeNames.Image.Jpeg);
         }