GPIO 8/9 were assigned to both LCD blue data and I2C touch,
causing I2C init to steal the LCD pins and blank the display.
Corrected to match Waveshare ESP32-S3-Touch-LCD-4.3 schematic.
Board selection driven by -DTARGET_E32R35T or -DTARGET_WAVESHARE_S3_43.
Defaults to E32R35T for backward compatibility.
All hardware pin definitions moved from Config.h to board headers.
SCREEN_WIDTH/SCREEN_HEIGHT now come from board headers.
Config.h is now purely application-level configuration.
New files:
BoardConfig.h — board selector
boards/board_e32r35t.h — E32R35T pins, display, touch config
boards/board_waveshare_s3.h — Waveshare S3 4.3" pins, display, touch config
Modified:
Config.h — removed hardware pins section, added #include BoardConfig.h,
added HOLD_DURATION_MS to timing section
