Seconds are now a setting: off, on shake (the default, unchanged), or always
on. Always on redraws the face every second and costs battery. Off drops the
shake handler entirely -- no seconds, and no backlight on a shake either.
The iMessage unread badge is now an explicit opt-in, off by default and marked
experimental. A theme or seconds change also takes effect immediately instead
of waiting for the next tick.
Theme is now Light, Dark, or Auto (switches at sunrise/sunset, computed
locally from your location -- no server round trip). The iMessage unread
badge also refreshes on a shake or double-tap now, not just once a minute,
so it catches up faster after the phone's been idle.
Added an iMessage unread badge to the header row, moved battery % and the
badge count to a segmented font, and dropped the battery icon and weather
alert icon to make room.