chore: add Ruff as a developer dependency

[bsoyka]

Not sure how strict you want Ruff to be—I've simply added it as a developer dependency so you can use it with its default settings.

Running checks and fixes makes no changes right now—the code already appears to be good according to the defaults.

Run these commands to lint and format:

uv run ruff check --fix
uv run ruff format

Closes: #3

[castroofelipee]

Thanks for your contribution! That was essential, it was exactly what we needed.