Migrates state/storage-explorer.tsx from offset/limit to cursor
pagination against the v2 objects endpoint, including search (v2's
prefix-match semantics are case-sensitive, unlike v1's ilike — an
accepted tradeoff). StorageColumn gains a cursor field; folder/file
merging is extracted into a shared formatFolderItemsV2 helper reused
by the picker dialogs. getAllItemsAlongFolder now walks v2 pages
instead of bumping an offset. Drops the "last accessed" sort option,
which v2 doesn't support.
PR 2 of 4 in the list-v2 migration (FE-4451), stacked on FE-4450.