Add SpoolBuddy quick menu with power control and system commands (#893)
Swipe down from the top of the SpoolBuddy display to open a quick-access
menu for toggling printer smart plugs and managing the device (restart
daemon, restart browser, reboot, shutdown). All destructive actions
require confirmation.
Backend: new POST /spoolbuddy/devices/{id}/system/command endpoint
queuing reboot/shutdown/restart_daemon/restart_browser commands.
Daemon: handles commands via subprocess (sudo reboot, systemctl restart).
Frontend: SpoolBuddyQuickMenu component, swipe-down gesture detection,
i18n keys for all 7 locales.