Add update job for `uv.lock`

[afuetterer]

We need a scheduled CI job to update the lockfile, similar to https://github.com/afuetterer/python-re3data/blob/main/.github/workflows/upgrade-requirements.yml

[afuetterer]

Waiting for dependabot to be able to do this.

https://docs.astral.sh/uv/guides/integration/dependency-bots/#dependabot

[afuetterer]

See https://docs.astral.sh/uv/guides/integration/dependency-bots/#dependabot

[afuetterer]

Actually this should be re-opened. dependabot only bumps "real" dependencies, not dev and other dependencies from dependency groups?

We still need an update job to run uv lock -U.