- Screen locker: disable VT switching (Ctrl+Alt+Fn) via setxkbmap
srvrkeys:none on startup; restore on close (production mode only).
Gracefully skips if setxkbmap is not installed (shutil.which).
Tests: 7 new tests, 100% branch coverage maintained.
- Midnight shutdown: restore real schedule values (Mon-Wed 21:00,
Thu-Sun 22:00, morning end 05:00); re-enable the three commented-out
leniency checks in check_schedule_protection(); self-lock script with
chattr +i at end of enable_midnight_shutdown().
- Hosts install: add UNBLOCK_STATE_FILE tracking for whitelisted domains;
check_unblock_entries_protection() blocks installation if the unblock
list grows; save state after install; self-lock install.sh and
generate_hosts_file.sh with chattr +i.
