Submit_Workflow hangs on submission

It hangs when attempting to submit to a namespace. URL opens, nothing is displayed. Env file created, but remains empty of info (just null strings)

```python
def _open_auth_url(auth_url: str, port: int) -> None:
httpd = _ReusingHTTPServer(("localhost", port), CallbackHandler)
webbrowser.open(auth_url)
try:
print(
f"Please authorize the application in your browser. If it does not open automatically, visit: {auth_url}"
)
httpd.handle_request()
os.environ["AUTH"] = httpd.auth_code
dotenv.set_key("src/.env", "AUTH", httpd.auth_code)

except OSError:
print("ERROR: Port in use. Please restart your terminal.")
os.environ["AUTH"] = ""
print("ERROR: Port in use. Please restart your terminal.")
exit(1)
finally:
print("Shutting down the server...")
httpd.socket.shutdown(socket.SHUT_RDWR)
httpd.server_close()
```
output:

(node:5049) [DEP0169] DeprecationWarning: `url.parse()` behavior is not standardized and prone to errors that have security implications. Use the WHATWG URL API instead. CVEs are not issued for `url.parse()` vulnerabilities.
(Use `node --trace-deprecation ...` to show where the warning was created)
Please authorize the application in your browser. If it does not open automatically, visit: https://identity.diamond.ac.uk/realms/dls/protocol/openid-connect/auth?client_id=workflows-cli&response_type=code&redirect_uri=http://localhost:8000/&scope=openid posix-uid profile email fedid&state=&nonce=&code_challenge=JVZHGbR1yQmIgn4MniLQK9xVmvIujWozvSgf0F6zhQI&code_challenge_method=S256

Seems to be hanging on handle request?

## Acceptance Criteria
- Specific criteria that will be used to judge if the issue is fixed

Start at _open_auth_url in the issue and trace how CallbackHandler supplies auth_code to httpd.handle_request(). Reproduce the submission flow and inspect why the localhost callback does not complete. Done means authorization returns successfully, AUTH is populated in the environment and src/.env, and submission continues instead of hanging.

由索引模型根据 Issue 内容生成。