Consider switching from pip-tools to uv

[StevenMaude]

uv is new-ish Python tooling that replaces pip, pip-tools, pyenv and virtualenv.

We may want to switch our tooling to use uv, because it could help simplify our developer setup. uv is a standalone binary compiled for Windows, macOS and Linux, and provides a way to install a specific Python version.

A current blocker is the lack of Dependabot support.

Before switching this template over to use uv, it's probably worthwhile trying out a switch on one or two projects first, before deciding on moving all active projects and this template to uv.