Add touch buttons for speaker toggle and music playback.

Enable SoftSPI touch, replace auto beeps with Speaker ON/OFF and Play Music controls, and document usage.

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

include/touch.h

@@ -0,0 +1,6 @@
+#pragma once
+
+#include <lvgl.h>
+
+void touch_init();
+void touch_read_cb(lv_indev_t *indev, lv_indev_data_t *data);