refactor(ui): apply code review fixes — bugs, risk, optimisations, cleanup

Fixes 7 bugs (timing UB on unsigned long, abs() no-op, XBM CRC PROGMEM
scan, CayenneLPP heap thrash ×2, UTF-8 reply prefix, lock-seq reset on
wake), 3 risk items (notif melody stop guard, bot trigger pre-lowercase,
lock-seq cleared on display wake), plus optimisations (fmtMsgAge/
getTextWidth caching, RTTTL builder consolidated to NodePrefs, HP_*
constants and homePageLabel table moved to NodePrefs, DataStore flat
lambda schema, translateUTF8Static factored out) and minor cleanup.

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

src/helpers/ui/DisplayDriver.h

@@ -6,6 +6,8 @@
 class DisplayDriver {
   int _w, _h;
 protected:
+  bool _vw_dirty = true;
+  bool _vw_result = false;
   DisplayDriver(int w, int h) { _w = w; _h = h; }
   void setDimensions(int w, int h) { _w = w; _h = h; }
 public:
@@ -151,8 +153,8 @@ public:
     }
   }
 
-  // convert UTF-8 to ASCII, transliterating accented/diacritic characters
-  virtual void translateUTF8ToBlocks(char* dest, const char* src, size_t dest_size) {
+  // convert UTF-8 to ASCII, transliterating accented/diacritic characters (callable without a display instance)
+  static void translateUTF8Static(char* dest, const char* src, size_t dest_size) {
     size_t j = 0;
     const uint8_t* p = (const uint8_t*)src;
     while (*p && j < dest_size - 1) {
@@ -178,6 +180,10 @@ public:
     }
     dest[j] = 0;
   }
+
+  virtual void translateUTF8ToBlocks(char* dest, const char* src, size_t dest_size) {
+    translateUTF8Static(dest, src, dest_size);
+  }
   
   // draw text with ellipsis if it exceeds max_width
   virtual void drawTextEllipsized(int x, int y, int max_width, const char* str) {
@@ -194,9 +200,11 @@ public:
     // for fixed-width fonts (OLED), keep tight spacing to save precious characters
     const char* ellipsis;
     // use a simple heuristic: if 'i' and 'l' have different widths, it's variable-width
-    int i_width = getTextWidth("i");
-    int l_width = getTextWidth("l");
-    if (i_width != l_width) {
+    if (_vw_dirty) {
+      _vw_result = (getTextWidth("i") != getTextWidth("l"));
+      _vw_dirty = false;
+    }
+    if (_vw_result) {
       ellipsis = "... ";  // variable-width fonts: add space
     } else {
       ellipsis = "...";   // fixed-width fonts: no space

src/helpers/ui/GxEPDDisplay.cpp

@@ -80,6 +80,7 @@ void GxEPDDisplay::startFrame(Color bkg) {
 
 void GxEPDDisplay::setTextSize(int sz) {
   _text_sz = sz;
+  _vw_dirty = true;
   display_crc.update<int>(sz);
   // Size 1 scales with orientation: 1× in portrait (≈OLED width), 2× in landscape.
   // Size 2 always uses 2× built-in (12×16) — fixed because layout Y-positions are hardcoded.
@@ -163,7 +164,7 @@ void GxEPDDisplay::drawXbm(int x, int y, const uint8_t* bits, int w, int h) {
   display_crc.update<int>(y);
   display_crc.update<int>(w);
   display_crc.update<int>(h);
-  display_crc.update<uint8_t>(bits, w * h / 8);
+  display_crc.update<uintptr_t>((uintptr_t)bits);
   uint16_t widthInBytes = (w + 7) / 8;
   for (uint16_t by = 0; by < h; by++) {
     for (uint16_t bx = 0; bx < w; bx++) {

src/helpers/ui/GxEPDDisplay.h

@@ -82,7 +82,7 @@ public:
     if (_text_sz == 2) return 16 * sc;
     return (_use_lemon ? 10 : 8) * sc;
   }
-  void setLemonFont(bool enabled) override { _use_lemon = enabled; }
+  void setLemonFont(bool enabled) override { _use_lemon = enabled; _vw_dirty = true; }
   bool isLemonFont() const override { return _use_lemon; }
   bool begin();
 

src/helpers/ui/SH1106Display.cpp

@@ -50,6 +50,7 @@ void SH1106Display::startFrame(Color bkg)
 void SH1106Display::setTextSize(int sz)
 {
   _text_sz = sz;
+  _vw_dirty = true;
   display.setTextSize(sz);
 }
 

src/helpers/ui/SH1106Display.h

@@ -50,7 +50,7 @@ public:
   uint16_t getTextWidth(const char *str) override;
   int getCharWidth() const override { return (_use_lemon ? 5 : 6) * _text_sz; }
   int getLineHeight() const override { return (_use_lemon ? 9 : 8) * _text_sz; }
-  void setLemonFont(bool enabled) override { _use_lemon = enabled; }
+  void setLemonFont(bool enabled) override { _use_lemon = enabled; _vw_dirty = true; }
   bool isLemonFont() const override { return _use_lemon; }
   void translateUTF8ToBlocks(char* dest, const char* src, size_t dest_size) override;
   void setBrightness(uint8_t level) override;