feat(federation): let Mastodon card external embeds — drop image attachments when a post has an embed
Mastodon shows EITHER media attachments OR a link preview card, never both. A post with an
external embed (Spotify/YouTube/SoundCloud/Vimeo/Bandcamp/Apple) plus a cover therefore showed the
cover and rendered the embed link as plain text — no player. Now, when the post has an embed link,
buildNote skips the image attachments so Mastodon renders the embed's player card. Klonkt's own
rendering is unchanged (cover + embed player still show on-site). Detection reuses
AudioEmbedService.detectProvider (single source of truth, covers all 6 providers).
- src/services/ActivityPubService.js — buildNote suppresses image attachments when an embed is present
Co-Authored-By: Claude <noreply@…>