Use uv for dependencies handling

[DarkaMaul]

Closes #30

This PR implements the following changes :

• Recommends to install uv and use it to run cookiecutter using uvx
• Uses uv venv to create the virtual env
• Uses uvx to build the package using build.
• Updates the ruff version
• Restricts the ruff checks to only src/ and test/ folders
• Update the GH Actions to run tests using uv too

Potential improvements :

• Rename the default virtual env name to .env and use the environment auto detection feature from uv.

[DarkaMaul]

Note to myself: not yet ready because workflows are not installing uv yet

Ready to review.

[woodruffw]

Thanks @DarkaMaul, great work! Looks like this sped up the selftests by over 4x, which is pretty crazy.