refactor(ui): shared drawList + header + key-decode helpers

- drawList(): scrollable list skeleton (visible window, keep-sel-in-view,
  scroll-column reserve, per-row callback, indicator). Migrate Tools, Bot,
  Nearby, Waypoints list and the three QuickMsg lists onto it; centralises the
  scroll-clamp/reserve/indicator that each had open-coded (and inconsistently).
- drawCenteredHeader(): centred title + separator, replacing the duplicated
  two-liner across ~10 screens (incl. QuickMsg, which used width()/2 spacing and
  was missed before); unifies the separator at headerH()-sepH().
- keyIsPrev()/keyIsNext() in UIScreen.h for the LEFT||PREV / RIGHT||NEXT idiom;
  applied to 6 screens, behaviour-preserving. Cancel/context-menu stay
  per-screen (they mean different things on different screens).
- rotLabel() dedups the 0/90/180/270 array in Settings.
- Unify selection-row height to lineStep()-1 (Tools/Bot matched the rest).

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

examples/companion_radio/ui-new/AutoAdvertScreen.h

@@ -30,8 +30,7 @@ public:
     int bar_h   = display.lineStep();
     int tip_y   = bar_y + bar_h + 4;
 
-    display.drawTextCentered(display.width() / 2, 0, "AUTO-ADVERT");
-    display.fillRect(0, display.headerH() - 1, display.width(), display.sepH());
+    display.drawCenteredHeader("AUTO-ADVERT");
 
     display.setCursor(2, label_y);
     display.print("Interval:");
@@ -56,8 +55,8 @@ public:
       _task->gotoToolsScreen();
       return true;
     }
-    bool right = (c == KEY_RIGHT || c == KEY_NEXT || c == KEY_ENTER);
-    bool left  = (c == KEY_LEFT  || c == KEY_PREV);
+    bool right = keyIsNext(c) || c == KEY_ENTER;
+    bool left  = keyIsPrev(c);
     if (right || left) {
       int idx = currentIdx();
       idx = right ? (idx + 1) % OPT_COUNT : (idx + OPT_COUNT - 1) % OPT_COUNT;