Uv migration and explicit LICENSE

[afrendeiro]

This is a maintenance PR which simplifies build/installation by migrating to uv and using a modern but pip-compatible pyproject.toml exclusively (no setup.py or setup.cfg).

A LICENSE file was added keeping the previous GPLv3+ license which was only mentioned in the package metadata and wasn't parsed by Github.

Some types were simplified and updated.

Dependency versions were updated and pinned if necessary.

[afrendeiro]

Hi @jkim810 would be good to have your eyes over this maintenance PR when you can

[jkim810]

Thank you so much for taking the time to updating the build to uv @afrendeiro !