Switch to uv

[ghickman]

This switches the project from using uv's pip and pip-compile interfaces to the full pyproject-configured usage.

Some benefits:

• All configuration is now in pyproject.toml, including the dependency specs from requirements.*.in
• uv run lets us treat virtualenvs and pythons as an implementation detail of the project, uv will make sure we have everything set up correctly
• The required python version is now defined in a standards-compliant fashion in the project block of pyproject.toml.

Note: dependency caching in CI is on by default on GitHub-hosted runners with setup-uv, which is why there is no caching configuration for that action.

[meshy]

@ghickman FYI the readme PR has been merged now.

[ghickman]

I couldn't remember where prod is these days, so I've explicitly removed the dev group in make build-prod with --no-dev. This is just a shorter version of --no-group dev, groups here refer to the PEP 735 dependency groups (yay standards!).