feat(ui): GPS breadcrumb phase 1 — storage, sampling, Summary view

Adds Tools › Breadcrumb. Enter on the screen toggles tracking; while
active, UITask::loop samples GPS at the cadence chosen in settings
(default 1 min) and drops the point into a 256-entry RAM ring guarded
by a min-distance gate (default 25 m). A "G" indicator joins "A" in
the status bar with the same blink convention.

New storage:
- examples/companion_radio/Breadcrumb.h — BreadcrumbStore class
- 256 × 12 B = 3 KB RAM (survives auto-off, lost on reboot — explicit
  flash-slot save comes in phase 4)
- Haversine min-delta gate, total distance, elapsed seconds, current
  km/h, bounding-box helper

New screen:
- examples/companion_radio/ui-new/BreadcrumbScreen.h — Summary view
  with Status, Points, Dist (m or km), Time (h:mm), Speed; Enter
  toggles tracking, Esc returns to Tools

Schema bump 0xC0DE0002 → 0xC0DE0003 for two new NodePrefs bytes:
breadcrumb_interval_idx (1min default) and breadcrumb_min_delta_idx
(25m default). Older saves leave both at zero, which matches the new
defaults. DataStore::loadPrefsInt/savePrefs read/write the pair.

Logging on/off is a runtime flag inside BreadcrumbStore — not a
preference — so reboot returns to the off state cleanly; the user
will be able to persist a snapshot to a slot in phase 4.

Phase 2 (map view), 3 (point list), 4 (slot save/load, GPX export over
USB), and 5 (settings UI) follow incrementally.

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

examples/companion_radio/ui-new/UITask.h

@@ -22,6 +22,7 @@
 
 #include "../AbstractUITask.h"
 #include "../NodePrefs.h"
+#include "../Breadcrumb.h"
 
 class UITask : public AbstractUITask {
   DisplayDriver* _display;
@@ -73,8 +74,11 @@ class UITask : public AbstractUITask {
   UIScreen* nearby_screen;
   UIScreen* dashboard_config;
   UIScreen* auto_advert_screen;
+  UIScreen* breadcrumb_screen;
   UIScreen* curr;
   CayenneLPP _dash_lpp;
+  BreadcrumbStore _breadcrumb;
+  uint32_t _next_breadcrumb_sample_ms = 0;
 
   void userLedHandler();
 
@@ -117,6 +121,8 @@ public:
   void gotoNearbyScreen();
   void gotoDashboardConfig();
   void gotoAutoAdvertScreen();
+  void gotoBreadcrumbScreen();
+  BreadcrumbStore& breadcrumb() { return _breadcrumb; }
   void playMelody(const char* melody);
   void stopMelody();
   bool isMelodyPlaying();