iTunes get_album_tracks called _lookup(id, entity='song') with no limit. The iTunes Lookup API
returns only 50 related entities unless limit is passed (max 200), so albums over 50 tracks showed
only the first 50 in the download window. Pass limit=200 on the main lookup AND the fallback-
storefront request.
Proven against the live iTunes API on the reporter's exact album (Frieren OST, id 1739445636,
70 tracks): no limit -> 50 songs, limit=200 -> 70 songs. Spotify already paginates; Deezer uses
limit=500 — iTunes was the only truncating source. Regression test asserts limit=200 is requested.
