refactor(ui): rename "Breadcrumb" to "Trail" across the feature

User-facing label change requested for the GPS trail viewer. Carries
through internally for consistency:
- Files: Breadcrumb.h → Trail.h, BreadcrumbScreen.h → TrailScreen.h
- Types: BreadcrumbPoint/Store/Screen → Trail*
- NodePrefs fields: breadcrumb_*_idx → trail_*_idx (same byte layout, no
  sentinel bump needed)
- UITask: _breadcrumb, breadcrumb_screen, gotoBreadcrumbScreen,
  _next_breadcrumb_sample_ms → trail-prefixed equivalents
- Tools menu label "Breadcrumb" → "Trail", screen title "TRAIL"

Status bar indicator stays "G" — semantics ("GPS logging active") match.

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

examples/companion_radio/ui-new/UITask.h

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