- Adds `cli/purge.php` so the purge policy can be applied from cron, mirroring `cli/db-optimize.php`.
- Documents it in `cli/README.md`.
Aims to be a small, contained answer to #3636: reuses the same `Feed::cleanOldEntries()` logic the GUI's "Purge now" button calls, packaged as a standard `cli/` script.
Mirror the existing db-optimize.php pattern so administrators can run the
purge policy on a schedule instead of waiting for the 1/30 random trigger
in feedController, or clicking 'Purge now' in the GUI.
The script applies the same archiving policy as the GUI button: per-feed
attribute, per-category attribute, then user config; with the existing
keep_favourites / keep_unreads / keep_labels / keep_min / keep_period /
keep_max guards. With no policy configured, it is a no-op.
Refs: https://github.com/FreshRSS/FreshRSS/issues/3636
Co-authored-by: Bjørn A. Andersen <polybjorn@users.noreply.github.com>
