TMDb's release_dates/content_ratings blocks were already fetched via
append_to_response but discarded at normalization -- every downstream
layer (ingestion write, repository read, schema, service) was unbuilt.
Adds the full pipeline: NormalizedReleaseDate + get_or_create_certification,
a shared polymorphic sync/read (movie and series both use it), and
MovieDetailOut/SeriesDetailOut certification + release_dates fields.
Series content_ratings has no date of its own, so each rating is anchored
to the show's first_air_date with release_type="tv".
Co-Authored-By: Claude Sonnet 5 <[email protected]>