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/models/movie.py

@@ -11,6 +11,7 @@ from sqlalchemy.orm import Mapped, mapped_column, relationship
 from app.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
 from app.models.collection import Collection
 from app.models.enums import MovieStatus
+from app.models.language_country import Certification
 
 
 class Movie(Base, UUIDPrimaryKeyMixin, TimestampMixin):
@@ -101,6 +102,8 @@ class ReleaseDate(Base, UUIDPrimaryKeyMixin):
     )
     note: Mapped[str | None] = mapped_column(Text, nullable=True)
 
+    certification: Mapped[Certification | None] = relationship()
+
 
 class MovieRecommendation(Base):
     """Recommendations/similar-title edges between movies."""