Purges records older than a configurable window (default 365d) once per day.
Also adds a composite index on device_events(mac_address, created_on DESC) for
efficient scan history queries at scale, and fixes a non-deterministic pagination
order by adding id as a tiebreaker to ORDER BY.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
