Add POST /playlists/{id}/items/bulk and /items/remove-bulk so a whole
season or show can be added/removed in one call (input order preserved,
duplicates skipped). Extend GET /playlists with contains_group=<rk,rk,…>
returning per-playlist group_in + a top-level group_size for the bulk
add-to-playlist dialog. Include the show's rating_key (show_id) on
playlist episode cards so the client can group a playlist by show/season.
peter
9c6f4b3923