Add lockfile for deploy/sync

[virtuald]

https://peps.python.org/pep-0751/ is a good place to start, hopefully there will be tooling that supports this soon... looks like there is some initial work at https://github.com/brettcannon/mousebender/tree/pep

[auscompgeek]

One of awkward parts is for a lockfile to make sense, it'll need to include the references to the robot platform wheels too. I'd be in favour of having a lockfile, but we'll need the tooling to allow that (which probably means exporting from uv won't work with our custom platform tags).