feat(audio): tracks without audio (link-only) — list with open-in links, no upload
You can now add a "Track without audio" in Admin → Audio (button) — only
title/artist + the Spotify/YouTube/SoundCloud links, no file. Such tracks
appear in albums & playlists (and standalone track embeds) in the list
with the open-in icons but WITHOUT a play button, and stay outside the
playback queue (which matches on URL). Lookups (posts album/single +
PlaylistService) no longer filter out fileless tracks. New route POST
/admin/audio/create-link. buster audio.css?v=9.
Co-Authored-By: Claude <noreply@…>