Fixing #82, preparing for new ui

[Rushmore75]

• I understand and have followed the contribution guide
• I have tested my changes locally and they are working as intended

I added new environment variables to https://github.com/revoltchat/frontend to to add better controls to where each server is commit. Also fixing #82, this probably isn't the most minimal possible config but it will get people going, lowering the barrier to entry 👍

[insertish]

Rejecting PR:

• The new frontend still has a while to go before it is put into production and the environment may still change before then, adding this now will just complicate matters.
• The Revolt.toml is purposefully not committed to this repository as it may change at any moment from the backend (tangent: we should probably have update notes for self-hosted so there is a clear migration path)
• Port changes are already covered in the FAQ: https://github.com/revoltchat/self-hosted?tab=readme-ov-file#putting-revolt-behind-another-reverse-proxy-or-on-a-non-standard-port