Add scheduled CI job to check for link rot in repo and website

Add a scheduled CI job that checks for broken or outdated links (link rot) in this repository and the [lima-vm.io](https://lima-vm.io/) website.

Instead of running this as part of the PR checks (which could be noisy or slow), the job could run once a day on a schedule. This would help us detect:

- Dead or redirected links in code files
- Broken links on the website (including external references)

*Originally posted by @jandubois in https://github.com/lima-vm/lima/pull/3633#pullrequestreview-2936385613*