feat: add periodic auto-advert with GPS position (Auto-Advert tool)

Adds configurable periodic 0-hop self-advert that includes GPS coordinates,
making the device's position visible in other nodes' Nearby Nodes screen.
Options: off / 1min / 2min / 5min / 10min / 30min / 1h.

Accessible via Tools → Auto-Advert. Timer runs in MyMesh::loop().

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

examples/companion_radio/ui-new/UITask.h

@@ -65,6 +65,7 @@ class UITask : public AbstractUITask {
   UIScreen* bot_screen;
   UIScreen* nearby_screen;
   UIScreen* dashboard_config;
+  UIScreen* auto_advert_screen;
   UIScreen* curr;
 
   void userLedHandler();
@@ -102,6 +103,7 @@ public:
   void gotoBotScreen();
   void gotoNearbyScreen();
   void gotoDashboardConfig();
+  void gotoAutoAdvertScreen();
   void playMelody(const char* melody);
   void stopMelody();
   bool isMelodyPlaying();