CI improvements

[thangleiter]

• Use micromamba. See https://github.com/marketplace/actions/setup-micromamba.
• Use uv. See https://github.com/marketplace/actions/astral-sh-setup-uv.
• Use pypa release tools. See https://packaging.python.org/en/latest/guides/publishing-package-distribution-releases-using-github-actions-ci-cd-workflows/.