[BUG] Authentication Flow Bug

[jeafreezy]

Describe the bug

If the user tries to authenticate using OSM OAUTH2.0, we don't have a specific callback route/modal/page dedicated to authentication, so when they are redirected back to fAIr, the 404 page is rendered briefly before getting redirected back to their initial page.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://fair.hotosm.org
2. Click on 'Log in' or log out if you're already logged in, then try to log in again.
3. See error.

Expected behavior
You should be authenticated smoothly without seeing the 404 page.

Screenshots

Screen.Recording.2025-02-22.at.16.05.39.mov

[jeafreezy]

The PR fixing this issue has just been merged. Kindly deploy to dev @kshitijrajsharma , so we can test. Thanks.