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/CompassScreen.h

@@ -31,8 +31,7 @@ public:
   int render(DisplayDriver& display) override {
     display.setTextSize(1);
     display.setColor(DisplayDriver::LIGHT);
-    display.drawTextCentered(display.width() / 2, 0, "COMPASS");
-    display.fillRect(0, display.headerH() - 1, display.width(), display.sepH());
+    display.drawCenteredHeader("COMPASS");
 
     const int hdr = display.headerH();
     const int cx  = display.width() / 2;