fix: make .ino compile guard target-aware

ST7796_DRIVER check only fires when USE_TFT_ESPI is active.
Waveshare (Arduino_GFX) path skips this check entirely.

sketches/doorbell-touch-esp32-32e/doorbell-touch-esp32-32e.ino

@@ -13,15 +13,17 @@
 #include "Config.h"
 #include "DisplayManager.h"
 #include "DoorbellLogic.h"
+#include "BoardConfig.h"
 
 #include <TFT_eSPI.h>
 #ifndef LOAD_GLCD
   #error "LOAD_GLCD is NOT defined — fonts missing!"
 #endif
-#ifndef ST7796_DRIVER
-  #error "ST7796_DRIVER is NOT defined — wrong setup!"
+#if USE_TFT_ESPI
+  #ifndef ST7796_DRIVER
+  #error "TFT_eSPI setup mismatch — ST7796_DRIVER expected for E32R35T"
+  #endif
 #endif
-
 #define HOLD_TO_SILENCE_MS 1000
 
 DoorbellLogic  logic;