Function flattenDonationPages

Flatten a TanStack-shaped paginated donation envelope ({ pages: [{ data: TiltifyDonation[] }, …] }) to a single sorted array. Handy for column scroll-lists and donor-feed panels that only need the row-level view.

• flipSorting: false (default) → newest first (completed_at desc).
• flipSorting: true → oldest first (completed_at asc).

null / undefined / missing-pages input returns []. Rows that don't structurally match a TiltifyDonation (missing id or amount) are dropped defensively.

For a stateful projection that preserves donations dropped from later pages (e.g. under maxPages), see useDonationsReducer in @playlive/react-query.