Update to NixOS 25.05 and more (MfGames Project Setup Flake)

Well, it's about time to update the flake to NixOS 25.05 just for general maintenance. There wasn't really anything special with this one, but we did have a couple minor and one big change:

• The conform settings did not put the scopes into the right place
• After experiencs, we added .cache to .gitignore
• When Rust is enabled, add target to .gitignore

The other big change is we are adding mfgames-conventional-commit as part of the flake. That way, we have a consistent method for updating version numbers based on conventional commits and it plays well with the intent we have with conform.