866392fecd
Audiobook and ebook libraries previously never entered the Recently Added pipeline: availability detection only ran for TV/movie/mixed libraries and release_events only knew episode/movie kinds, so server channels (Discord/generic webhooks) could not announce new audiobooks or ebooks. Generalize the movie path into a flat-item-kind registry (internal/notifications/item_kind.go) driving availability detection, recording, channel toggles, payload rendering, test fixtures, and the admin backfill seeder. New kinds share a kind-discriminated item_availability table; movie_availability stays as-is. Channels gain notify_new_audiobooks/notify_new_ebooks toggles (default on, additive API fields) and embeds carry the author from item_people. Flood-safe by construction: existing libraries seed silently on their first post-upgrade full scan. Extract internal/librarykind to replace the is*LibraryType helper copies that had drifted across scanner, libraryingest, and metadata (metadata's movie check silently included mixed; now spelled explicitly). Co-authored-by: Claude Fable 5 <noreply@anthropic.com>