use correct HTTP status code to force GET requests

src/backend/utils.ts

@@ -36,5 +36,5 @@ export const rewriteQueryParamsWith = (req: Request, res: Response, newParams: R
     newQuery.set(param, value);
   }
 
-  res.redirect(`?${newQuery.toString()}`);
+  res.redirect(303, `?${newQuery.toString()}`);
 };