feat: pause Today during mobile device setup (Closes #1084)

frontend/index.html

@@ -95,6 +95,10 @@
       </div>
       <button id="close-device-setup" type="button" aria-label="Close device setup">Close</button>
     </div>
+    <aside class="today-detour-interruption" id="device-setup-today-detour" data-today-detour role="status" aria-live="polite" hidden>
+      <strong data-today-detour-label>Today paused</strong>
+      <button id="return-from-device-setup" data-return-from-detour type="button">Return to Today</button>
+    </aside>
     <ol class="device-setup-list">
       <li class="device-setup-step">
         <div><strong>Install Stackchain</strong><p class="small" id="device-setup-install-status" role="status"></p></div>