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/DashboardConfigScreen.h

@@ -46,8 +46,7 @@ public:
     int start_y = display.listStart();
     int val_x   = display.valCol();
 
-    display.drawTextCentered(display.width() / 2, 0, "CLOCK FIELDS");
-    display.fillRect(0, display.headerH() - 1, display.width(), display.sepH());
+    display.drawCenteredHeader("CLOCK FIELDS");
 
     static const char* labels[] = { "Field 1", "Field 2", "Field 3" };
     for (int i = 0; i < FIELD_SLOTS; i++) {
@@ -72,8 +71,8 @@ public:
     }
     if (c == KEY_UP   && _sel > 0)              { _sel--; return true; }
     if (c == KEY_DOWN && _sel < FIELD_SLOTS - 1){ _sel++; return true; }
-    if (c == KEY_LEFT  || c == KEY_PREV)  { cycle(_sel, -1); return true; }
-    if (c == KEY_RIGHT || c == KEY_NEXT)  { cycle(_sel,  1); return true; }
+    if (keyIsPrev(c))  { cycle(_sel, -1); return true; }
+    if (keyIsNext(c))  { cycle(_sel,  1); return true; }
     if (c == KEY_ENTER)                   { cycle(_sel,  1); return true; }
     return false;
   }