Adds opt-in (default OFF) auto-lock: after X minutes of no user input
the app calls signOut() (full memory wipe + PIN re-entry on next open).
Settings dropdown (Aus / 5 / 15 / 30 / 60 min) lives in SecurityCenter
below the existing wipe-on-close toggle. The idle timer is mounted in
AppShell via useIdleAutoLock; activity events are throttled to 1 Hz to
avoid timer thrash on rapid mouse movement. The localStorage key is
added to PRESERVE_LOCAL_STORAGE so a wipe never silently disables the
feature.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
byGalax