Use of uv instead of pip

[asdkant-bf]

Problem statement

pip is slow, uv is FAST and fairly well battle-tested, and in CI runs speed is good.

Using uv should be a fairly painless since it provides a drop-in replacement for the pip CLI

Solution brainstorm (optional)

have a switch in the init subcommand to use uv, or just straight up use it instead of `pip

It looks like the changes would be for this file, in particular the general python installation logic (so it includes uv) and the env and dependency handling logic so it calls uv instead of pip and the regular venv commands