https://github.com/meshcore-dev/MeshCore/issues/989 - persist GPS enabled state to preferences

Add GPS configuration to NodePrefs structure and persist the GPS
enabled state when toggled via UI. This ensures GPS settings are
retained across device restarts.

examples/companion_radio/ui-new/UITask.cpp

@@ -863,13 +863,16 @@ void UITask::toggleGPS() {
       if (strcmp(_sensors->getSettingName(i), "gps") == 0) {
         if (strcmp(_sensors->getSettingValue(i), "1") == 0) {
           _sensors->setSettingValue("gps", "0");
+          _node_prefs->gps_enabled = 0;
           notify(UIEventType::ack);
           showAlert("GPS: Disabled", 800);
         } else {
           _sensors->setSettingValue("gps", "1");
+          _node_prefs->gps_enabled = 1;
           notify(UIEventType::ack);
           showAlert("GPS: Enabled", 800);
         }
+        the_mesh.savePrefs();
         _next_refresh = 0;
         break;
       }