New AddToQueue appends to an already-active session without touching
voice (the dashboard can't join a channel on its own), and add_song's
dispatch case now branches: a voice_channel_id in the payload means
"start fresh", so it goes through EnqueueAndPlay (join + play) instead.
Query normalization (plain text -> YouTube search, stripping
autoplay/radio params off pasted YouTube URLs) moves out of /play's
handler into a shared NormalizeQuery, both entry points need it, not
just one.
Starting playback from the dashboard also posts the now-playing embed
into the voice channel's own built-in text chat, matching what /play
already does, instead of leaving it with nowhere to show up.
FernandoJVideira
da66eb8dd5