Brush up on `uv` -> add more support?

[mbercx]

See the following PR on qe-tools: aiidateam/qe-tools#144

Learn more about uv vs Hatch development workflows; decide what is right for my packages / support both / have copier question.

[mbercx]

A few notes already:

1. For sure I want to switch to straight uv only for the CI. Hatch has been too flaky.
2. I still like Hatch for tox-like features. Doing hatch run bump minor is just good fun.
3. I'm not sure if we need to commit a uv.lock in most of my repos. So I would add that to .gitignore by default. uv-happy developers can still uv sync etc.