mvmOS 0.40.0-beta: Cron Manager joins the desktop

Cron Manager — view, add, edit, enable, disable and run cron jobs, plus toggle the built-in mvmOS Scheduler — now ships with every installation's desktop instead of needing a separate Store install. Toggling the scheduler now asks for password confirmation like every other privileged action, and always targets only this installation's own scheduler tick, even when several mvmOS installs share one server. The subscription page now shows how many days are left on an active premium key next to its expiry date, server timezone detection returns a proper zone name the browser accepts instead of a local abbreviation, and a premium key that stops validating — expired, revoked, or replaced elsewhere — now always clears its locally cached premium code.