Before #753 dedup_hash included price, so each price change created a new
active row. The canonical rows are now upserted correctly; ghost rows sit
frozen with stale hashes. Deactivates only active non-canonical rows in
groups that already have a canonical twin, excluding all-ghost groups.
Dry-run on prod (2026-06-16): UPDATE 167 rows as expected (yandex ~164,
cian ~1, n1 ~2, avito 0).
Refs #753