Expose certifications and per-country release dates

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]>

app/services/ingestion/movie_ingestion.py

@@ -249,6 +249,9 @@ async def ingest_movie(
         artwork_list=normalized.artwork,
     )
     await _replace_movie_videos(session, movie.id, tmdb_provider.id, normalized.videos)
+    await polymorphic.sync_release_dates(
+        session, entity_type="movie", entity_id=movie.id, release_dates=normalized.release_dates
+    )
     await _link_external_ids(session, movie.id, tmdb_provider.id, normalized)
 
     await session.execute(

app/services/ingestion/series_ingestion.py

@@ -244,6 +244,9 @@ async def ingest_series(
         artwork_list=normalized.artwork,
     )
     await _replace_entity_videos(session, "series", series.id, tmdb_provider.id, normalized.videos)
+    await polymorphic.sync_release_dates(
+        session, entity_type="series", entity_id=series.id, release_dates=normalized.release_dates
+    )
 
     for stub in normalized.seasons:
         season = await tv_repository.get_or_create_season(session, series.id, stub.season_number)