Add an overlay soundboard and fix playback command bugs.

Stop was advancing the queue, history overwrote the day file, and slash commands often never replied; soundboard clips now mix on top of the current track.

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

src/commands/stop.ts

@@ -14,6 +14,7 @@ function register() {
 async function execute(interaction: ChatInputCommandInteraction<CacheType>) {
     try {
         stop_playback(player)
+        await interaction.reply('Zatrzymane, kolejka wyczyszczona')
     } catch (error) {
         console.error(error);
         await interaction.reply('Coś poszło nie tak :/');