feat: Make lock screen a page type and display title bar on it
Moves lock-screen rendering out of a dedicated branch in UITask::loop()
into a proper HomePage::LOCK page in HomeScreen (appended after Count,
so no existing HomePage/home_pages_mask bit shifts), adds a title bar to
the lock screen (node name omitted, intentionally, for at-a-glance
anonymity), and makes drawClockTime()'s center-alignment opt-in so the
lock screen can left-align its clock. Reviewed: the two existing
drawClockTime() call sites are both updated to keep their prior
alignment, and this doesn't interact with our home_pages_mask=0 default,
msg_wake_screen_off, or the shutdown()-flush fix landed this cycle.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>