chagne gpt-4.1 as default model

app.py

@@ -311,7 +311,7 @@ def grade(file_obj, key, model, progress=gr.Progress()):
             zipObj.write(fpath, arcname)
     for fpath in files:
         os.remove(fpath)
-    schedule_cleanup([zip_file, workdir], delay=600)
+    schedule_cleanup([zip_file, workdir], delay=3600)
     return zip_file