Switch to `uv`

[annehaley]

This metadata at the top is from PEP 723. It's meant to be similar to a pyproject.toml and includes the requirements for running the script independently. If you use uv run --script sentinel2Download.py, it will automatically create a venv and install the dependencies.

I think at some point UVDat as a whole should be updated to us uv, which is in line with the updated resonant stack.

Originally posted by @BryonLewis in #186 (comment)

[annehaley]

Completed in #225