feat: add touch driver abstraction layer

XPT2046 path: no change — uses TFT_eSPI built-in getTouch().
GT911 path:   TouchDriver namespace with begin()/read() stub.

TouchDriverGT911.cpp compiles to nothing on TFT_eSPI targets.
Uncomment TAMC_GT911 lines to enable real capacitive touch.

sketches/doorbell-touch-esp32-32e/TouchDriver.h

@@ -0,0 +1,21 @@
+#pragma once
+#include "BoardConfig.h"
+
+// ═══════════════════════════════════════════════════════════════════
+// Touch driver abstraction
+//
+// XPT2046: integrated in TFT_eSPI — DisplayManager calls
+//          _tft.getTouch() / _tft.setTouch() directly inside
+//          #if USE_TOUCH_XPT2046 blocks.
+//
+// GT911:   separate I2C controller — namespace below.
+// ═══════════════════════════════════════════════════════════════════
+
+#if USE_TOUCH_GT911
+
+namespace TouchDriver {
+  void begin();
+  bool read(uint16_t &x, uint16_t &y);
+}
+
+#endif

sketches/doorbell-touch-esp32-32e/TouchDriverGT911.cpp

@@ -0,0 +1,42 @@
+#include "BoardConfig.h"
+
+#if USE_TOUCH_GT911
+
+#include "TouchDriver.h"
+#include <Wire.h>
+
+// ═══════════════════════════════════════════════════════════════════
+// GT911 capacitive touch — Waveshare ESP32-S3 Touch LCD 4.3"
+//
+// This is a compilable stub.  To enable actual touch:
+//   1. arduino-cli lib install "TAMC_GT911"
+//   2. Uncomment the TAMC_GT911 lines below.
+// ═══════════════════════════════════════════════════════════════════
+
+// #include <TAMC_GT911.h>
+// static TAMC_GT911 ts(TOUCH_SDA, TOUCH_SCL, TOUCH_INT, TOUCH_RST,
+//                      SCREEN_WIDTH, SCREEN_HEIGHT);
+
+namespace TouchDriver {
+
+void begin() {
+  Wire.begin(TOUCH_SDA, TOUCH_SCL);
+  // ts.begin();
+  // ts.setRotation(TOUCH_MAP_ROTATION);
+  Serial.println("[TOUCH] GT911 stub initialized");
+}
+
+bool read(uint16_t &x, uint16_t &y) {
+  // ts.read();
+  // if (ts.isTouched) {
+  //   x = ts.points[0].x;
+  //   y = ts.points[0].y;
+  //   return true;
+  // }
+  (void)x; (void)y;
+  return false;
+}
+
+} // namespace TouchDriver
+
+#endif // USE_TOUCH_GT911