Restore TF card UI and speaker at 20% volume.

Keep calibrated SoftSPI touch mapping unchanged.

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

include/audio_test.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <Arduino.h>
+
+void audio_init();
+
+void audio_set_enabled(bool on);
+bool audio_is_enabled();
+
+// 音量 0–100，默认 20
+void audio_set_volume(uint8_t percent);
+uint8_t audio_get_volume();
+
+void audio_play_music();
+void audio_stop();
+bool audio_is_playing();
+
+void audio_tick();
+
+const char *audio_last_status();