feat: add remote device settings portal and Pi hot reload

- add /settings/device portal page and portal device-config GET endpoint
- add portal navigation and client-side device settings editor UI
- hot-reload Account/Car display config after local saves and server syncs
- document portal workflow and Phase 25.5b completion
- add runtime reload tests for account, car, and sync callback

Co-authored-by: Copilot <[email protected]>

server/templates/base.html

@@ -49,6 +49,11 @@
                     <i class="fas fa-video fa-fw"></i><span>Dashcam archive</span>
                 </a>
             </li>
+            <li class="nav-item">
+                <a class="nav-link{% if request.endpoint == 'portal_device_settings_page' %} active{% endif %}" href="{{ url_for('portal_device_settings_page') }}">
+                    <i class="fas fa-sliders-h fa-fw"></i><span>Device settings</span>
+                </a>
+            </li>
         </ul>
         <div class="px-3 pb-2 mt-auto text-muted d-flex align-items-center gap-1 sidebar-user-footer" style="font-size:.75rem;">
             <i class="fas fa-user fa-fw flex-shrink-0"></i>
@@ -108,6 +113,10 @@
             <i class="fas fa-video"></i>
             <span>Dashcam</span>
         </a>
+        <a class="mobile-nav-item{% if request.endpoint == 'portal_device_settings_page' %} active{% endif %}" href="{{ url_for('portal_device_settings_page') }}">
+            <i class="fas fa-sliders-h"></i>
+            <span>Device</span>
+        </a>
         <a class="mobile-nav-item" href="{{ url_for('logout') }}">
             <i class="fas fa-sign-out-alt"></i>
             <span>Logout</span>