Make the device status card always visible, not just on Stats

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.

server/app/templates/app_base.html

@@ -72,6 +72,7 @@
             <button type="button" id="theme-toggle" class="icon-btn" title="Toggle dark mode" aria-label="Toggle dark mode">🌓</button>
           </div>
         </div>
+        {% block device_status %}{% endblock %}
         {% block tabs %}{% endblock %}
         {% block content %}{% endblock %}
       </main>