The realtime FK mirror (base.py:607-616) only landed 2026-06-17 (e63b21e).
Listings matched into house_sources before that — notably 9205 cian novostroyki
frozen at 2026-05-31 — never had house_id_fk mirrored back, breaking the
canonical "same-building via house_id_fk" estimator path (93% of active cian
novostroyki had NULL fk citywide).
Add data/sql/130_backfill_listings_house_id_fk.sql: deterministic source-id
backfill via house_sources (ext_source, ext_id → house_id), idempotent
(WHERE house_id_fk IS NULL), no fuzzy/address fallback. Prod (read-only):
9235/9235 target rows resolve deterministically, zero unresolvable. One-time
backlog drain; future rows linked in realtime by the e63b21e mirror.
