🔒 OAuth Required 📄 Pagination

Paginated item array for a sync, scoped to the authenticated user — foreign ids return 404. Split out because a single sync can hold thousands of items.

Skipped items mix history and rating (see each item's kind discriminator). Each item is the raw stored item (so source-specific fields are preserved) plus a normalized envelope, with timestamps normalized to .000Z. Pagination and X-Pagination-* headers are identical to the list endpoint.