List a diary's photos, newest first (Media view, issue #1520)

Keyset pagination over the diary's ENTRIES, newest first, flattened to the media each one holds -- same ACL, same Free-plan 30-day history cutoff and same Time-Capsule rule as GET /entries (a still-sealed entry contributes nothing). limit therefore counts entries, not pictures: a page may come back with fewer than limit items, or with none at all, while pagination.hasNext is still true -- that is a stretch of diary written without a camera, not the end of the grid. Keep paging until hasNext is false. The pictures themselves are resolved by the client through GET /media/{mediaAssetId}.