Pin or lower bound the version of uv

[nathanjmcdougall]

Motivation
This is now supported via astral-sh/uv#10248. I think we want to pin since breaking changes may occur e.g. the move from ~/.cargo to ~/.local

Summary of desired enhancement
This will allow a sync with hard-coded versions in CI and/or pre-commit to ensure consistency. It will also ensure consistency between devs, and protect from breaking changes.

However, it's not clear whether the above will enforce the version in the sense of automatically updating itself to give a compatible verison, or whether it will just abort on failure. This needs to be investigated, if the latter then we will need some bootstrapping logic to automatically download the pinned version etc.