fix(ui): standardize context menu cycling + PopupMenu height clamping

PopupMenu:
- _cap now uses max_by_height as a hard ceiling (never draw outside screen).
  Previously max(_visible, max_by_height) let callers exceed the screen on
  OLED 64px. Now: OLED→4 items, landscape e-ink→10, portrait e-ink→22.

QuickMsgScreen:
- Contact context menu: Notif and Melody cycle with LEFT/RIGHT in-place;
  ENTER closes without re-cycling.
- Channel context menu: Notif, Melody and Fav same pattern.

RingtoneEditorScreen:
- Migrated from bespoke menu to PopupMenu (same pattern as everywhere else).
- Duration (1/4…1/32) and BPM (60…180) are now single rows that cycle with
  LEFT/RIGHT; separate BPM+/BPM- rows removed.
- Fixed _menu_dur_label buffer too small for "Duration: 1/16" (14→16 bytes).

NearbyScreen:
- Removed redundant "Back" item from context menu (Cancel key navigates back).

TrailScreen:
- Grid toggle responds to LEFT/RIGHT in addition to ENTER.
- Export labels: "Export GPX (live/saved)" → "Export (live/saved)" to fit PM_BW.

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

examples/companion_radio/ui-new/PopupMenu.h

@@ -35,11 +35,12 @@ struct PopupMenu {
   }
 
   int render(DisplayDriver& display) {
-    // On tall displays (portrait e-ink) show as many items as fit;
-    // on small displays fall back to the caller-specified _visible cap.
+    // Hard ceiling: never show more items than physically fit on screen.
+    // On tall displays (portrait e-ink) this expands beyond _visible;
+    // on small displays (OLED 64px) it clamps below _visible.
     int max_by_height = (display.height() - PM_BY - 12) / PM_ITEM_H;
     if (max_by_height < 1) max_by_height = 1;
-    _cap = (max_by_height > _visible) ? max_by_height : _visible;
+    _cap = max_by_height;
     int vis = (_count < _cap) ? _count : _cap;
     int bh  = 12 + vis * PM_ITEM_H;