Switch to uv

[zerolab]

Used https://github.com/mkniewallner/migrate-to-uv via uvx migrate-to-uv

Some timings using time <command>

poetry install       5.85s user 3.40s system 101% cpu 9.124 total
uv sync              0.87s user 1.91s system 137% cpu 2.027 total

and subsequent calls (with reinstalls, https://docs.astral.sh/uv/concepts/cache/)

uv sync --refresh    0.40s user 0.33s system  67% cpu 1.070 total
uv sync --reinstall  0.43s user 1.03s system 87% cpu 1.664 total