fix: adopt potentially changed file extension when downloading

src/Controller/Administrative/Document/BatchDownloadController.php

@@ -59,6 +59,12 @@ class BatchDownloadController extends AbstractController
                 /** @var Upload $upload */
                 $filename = $upload->getOriginalFilename();
                 $filepath = $this->uploadHandler->getUploadFilepath($upload);
+                $extension = pathinfo($filepath, PATHINFO_EXTENSION);
+
+                // adopt potentially changed file extension
+                if (false === str_ends_with($filename, $extension)) {
+                    $filename = $filename.'.'.$extension;
+                }
 
                 try {
                     $zip->addFileFromPath(fileName: $filename, path: $filepath);
@@ -79,4 +85,4 @@ class BatchDownloadController extends AbstractController
 
         return $response;
     }
-}
+}