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>

src/helpers/ui/DisplayDriver.h

@@ -185,6 +185,15 @@ public:
     fillRect(0, hdr - 1, width(), sepH());
   }
 
+  // Centred screen title + bottom separator line — the standard top bar for
+  // full-screen list/detail views. Leaves ink LIGHT; callers can draw extra
+  // header content (counters, etc.) afterwards.
+  void drawCenteredHeader(const char* title) {
+    setColor(LIGHT);
+    drawTextCentered(width() / 2, 0, title);
+    fillRect(0, headerH() - sepH(), width(), sepH());
+  }
+
   // Advance a UTF-8 pointer by one codepoint, returning the decoded value.
   // Invalid sequences return 0xFFFD and consume trailing continuation bytes.
   static uint32_t decodeCodepoint(const uint8_t*& p) {

src/helpers/ui/UIScreen.h

@@ -14,6 +14,12 @@
 #define KEY_PREV           0xF2
 #define KEY_CONTEXT_MENU   0xF3
 
+// "Previous"/"Next" navigation keys: the directional key and its rotary-encoder
+// twin. Decrement / increment a value, or step a selection. (Cancel and the
+// context-menu key stay screen-specific — they mean different things per screen.)
+static inline bool keyIsPrev(char c) { return c == KEY_LEFT  || c == KEY_PREV; }
+static inline bool keyIsNext(char c) { return c == KEY_RIGHT || c == KEY_NEXT; }
+
 #ifndef JOYSTICK_ROTATION
   #define JOYSTICK_ROTATION 0
 #endif