Moved out of the Stats tab's side column into a new horizontal bar
shared by every frame page (Photos/Configuration/Stats), sitting
between the page title and the tabs so it's on screen regardless of
which tab is active.
_device_status_bar.html is a new partial included via a device_status
block in app_base.html; device_status_bar.js is the fetch/render/poll
logic extracted from frame_stats.js and adapted to a wrapping row of
label/value pairs instead of a stacked list. frame_stats.html's Device
card and now-single-card .side-col are gone -- Battery history and
Lifetime stats just stack directly.
