Add touch-to-logical coordinate mapping for UI

Implements tapToLogical() to convert normalized touch coordinates to orientation-aware logical screen coordinates. Adds TouchRegistry hit testing for interactive UI elements and header back button. Touch gestures now work correctly across all screen orientations (Portrait, Landscape, etc.) by inverting the rotateCoordinates transform.

lib/hal/HalGPIO.h

@@ -77,6 +77,9 @@ class HalGPIO {
   // primitive; see MappedInputManager for the top-left = Back mapping.)
   bool wasTouchTap(float& nx, float& ny) const;
 
+  // True if a touch controller is present/active (runtime gate; false on the C3).
+  bool hasTouch() const;
+
   // Setup wake up GPIO and enter deep sleep
   void startDeepSleep();