fix(home-pages): stop Favourites re-enabling on update; add Map visibility toggle

The prefs schema-migration block runs on every SCHEMA_SENTINEL mismatch, and
the "turn Favourites on" step was ungated. Since each firmware release bumps
the sentinel, every update re-applied `home_pages_mask |= HP_FAVOURITES`,
clobbering a user who had hidden it. Gate it to the transition that added
Favourites (sentinel < 0xC0DE0002), matching the trail_units_idx migration.

The Map/Trail carousel page shipped with no visibility toggle: pageBit(MAP)
returned -1 so it was always visible with no Settings row. Add a proper "Map"
toggle (new HPB_MAP/HP_MAP bit, pageBit/bitToPage cases, HOME_MAP settings
row) plus a gated one-time migration (sentinel < 0xC0DE0018) that keeps it
visible for upgraders. Bump SCHEMA_SENTINEL to 0xC0DE0018; page_order[] stays
a literal 11 so the persisted layout is unchanged.

Also fix the fresh-install seed, which used a stale 0x01FF literal that left
Favourites hidden on new installs despite its "all pages visible" comment;
seed NodePrefs::HP_ALL so fresh installs match upgraders (Favourites + Map).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

examples/companion_radio/ui-new/UITask.cpp

@@ -359,6 +359,7 @@ class HomeScreen : public UIScreen {
 #endif
     if (page == TOOLS)     return NodePrefs::HPB_TOOLS;
     if (page == SHUTDOWN)  return NodePrefs::HPB_SHUTDOWN;
+    if (page == MAP)       return NodePrefs::HPB_MAP;
     return -1;  // SETTINGS, QUICK_MSG always visible (no mask bit)
   }
 
@@ -382,6 +383,7 @@ class HomeScreen : public UIScreen {
       case NodePrefs::HPB_SHUTDOWN:  return SHUTDOWN;
       case NodePrefs::HPB_SETTINGS:  return SETTINGS;
       case NodePrefs::HPB_QUICK_MSG: return QUICK_MSG;
+      case NodePrefs::HPB_MAP:       return MAP;
       default: return -1;
     }
   }