System health checks

[stevenle]

Description

We should have some way of performing health checks on the overall project, e.g. ensuring security rules are up-to-date and notifying clients if a newer version of the CMS is available.

This should run on some regular interval (e.g. once per week) and can either be run when a dev server is started or via a cron job. If the health checks are run async via cron jobs, it should notify via a UI announcement (see #908) with some button to help fix issues.