Data layer for the 'complete your collections' gap engine. People/credits/genres are already
normalized + indexed, so the only missing signal was franchise membership:
- movies: + tmdb_collection_id (indexed) + tmdb_collection_name (schema + _COLUMN_MIGRATIONS,
SCHEMA_VERSION 17->18, _ENRICH_META_COLS whitelist so enrichment_apply backfills them)
- enrichment match() reads belongs_to_collection (a standard movie-detail field, no extra call)
and writes the id/name into the match metadata.
Additive + backfill-only (COALESCE), nothing existing rewired. (also noqa'd a pre-existing
OMDb S110 in the touched file to keep ruff clean.)
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