How to add categories? auth redirect URL and playfab guidance

[osaket]

So I cloned the repo - and currently stuck at three points:

1. How do we go about adding a new category (as is a requirement for posting a new model/article? Currently shows blank with no way to add a new category?
2. Leaderboard doesnt seem to work out of the box even after adding Playfab credentials in .env - any documentation here would be super helpful.
3. Lastly, for running local host what is the best redirect URL to choose when using social login/auth for discord/github etc?

Many thanks for sharing this awesome project - hope my questions are not repeats from prior discussions.