fix(map): persist pager map view state (#48)

Preserve the real ESP/Pager GPS map runtime view state across menu exit and re-entry by caching zoom, center, pan, and follow mode outside the reset GPSPageState lifecycle and updating the cache when map controls, touch pan, route focus, tracker focus, or GPS follow refresh change the view.

modules/ui_shared/include/ui/screens/gps/gps_page_runtime.h

@@ -8,5 +8,7 @@ namespace gps::ui::runtime
 bool is_available();
 void enter(const shell::Host* host, lv_obj_t* parent);
 void exit(lv_obj_t* parent);
+void remember_gps_view_state();
+bool restore_gps_view_state();
 
 } // namespace gps::ui::runtime