Query key for the global source_id → status map. Backend rows are keyed per
(reading list, paper); PUT fans one write out to every list the paper is on
and GET aggregates back to one status per paper — see
crates/core/src/service/reading_list.rs for the keying contract.
Query key for the global source_id → status map. Backend rows are keyed per (reading list, paper); PUT fans one write out to every list the paper is on and GET aggregates back to one status per paper — see
crates/core/src/service/reading_list.rsfor the keying contract.