feat: prevent reversing directly into snake neck and play denied sound effect

include/game_audio.h

@@ -12,6 +12,7 @@ struct AudioContext {
     mm_sound_effect sfx_unpause;
     mm_sound_effect sfx_plop;
     mm_sound_effect sfx_fail;
+    mm_sound_effect sfx_denied;
 };
 
 void audio_setup(AudioContext &audio);
@@ -26,6 +27,7 @@ void audio_play_plop(const AudioContext &audio);
 void audio_play_pause(const AudioContext &audio);
 void audio_play_unpause(const AudioContext &audio);
 void audio_play_fail(const AudioContext &audio);
+void audio_play_denied(const AudioContext &audio);
 
 bool audio_toggle_music(AudioContext &audio);
 bool audio_is_music_enabled(const AudioContext &audio);