Return the ids of every selectable item matching the All-expenses filters.

Backs the "select all expenses" header checkbox, which materialises the full matching id set into its selection so the existing bulk-by-ids actions apply across every page, not just the visible 200. Uses the same filter builder (and the same read auth) as :func:list_items.

Journal-only by design: synthesised salary rows are read-only / never selectable, so they're excluded here — and skipping the salary synthesis pass keeps this endpoint a single cheap query.