use env hf_token for file upload

app.py

@@ -112,6 +112,7 @@ def upload_certificate_to_hub(username: str, certificate_img) -> str:
                 path_in_repo=path_in_repo,
                 repo_id=repo_id,
                 repo_type="dataset",
+                token=os.getenv("HF_TOKEN"),
             )
 
             # Construct the URL to the image