chore: fix phpstan errors

src/Controller/Booking/DownloadController.php

@@ -49,6 +49,7 @@ class DownloadController extends AbstractController
         $type = match ($fileType) {
             'documents' => 'Dokumentdruck',
             'invoice' => 'Vorgangdruck',
+            default => throw new \InvalidArgumentException(sprintf('Unknown file type: %s', $fileType)),
         };
 
         $this->logger->info('Initiated document download', [