fix 3.5 backlight and GT911 for cyd_35r.

TFT_BL was wrongly GPIO21 (GT911 INT); use GPIO27, DRAW_BUF_DIV=20, and export firmware/cyd_35r.

Co-authored-by: Cursor <cursoragent@cursor.com>

include/touch.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include <lvgl.h>
+#include <stdint.h>
+
+void touch_init();
+void touch_read_cb(lv_indev_t *indev, lv_indev_data_t *data);