Replace manual forEachUser pattern with built-in sharedModules for
applying config to all home-manager users. Add automatic garbage
collection of old generations (weekly, older than 7 days) and remove
the now-unnecessary expire-home-manager-generations justfile recipe.
Also update codex PR patch hash (upstream patch was modified).
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
