[willmakenoise]

Problem

Search results (Movie, TV) and detail lookups (MovieDetails, TVDetails) don't expose poster/backdrop images, even though the API returns them. Movie also doesn't expose a release date, even though MovieDetails already does.

Confirmed against the existing test fixtures (tests/fixtures/*/search_1.json, search_2.json, movie.json, tv.json) — posterPath, backdropPath, and (for search results) releaseDate are all present in real API responses, just not modeled.

Change

• Movie, TV: add poster_path/backdrop_path (optional — posterPath is frequently null in practice).
• Movie: add release_date (date | None). The API can send "" rather than omitting the field when unknown, so this uses the same deserialize_optional_date approach Handle empty TV first air dates #496 added for TV.first_air_date, treating an empty string as None instead of failing date.fromisoformat.
• MovieDetails, TVDetails: add poster_path/backdrop_path for the same reason.

Testing

• Snapshot file updated (--snapshot-update); diff is purely additive/type-representation only — no existing fields changed or removed, aside from Movie.release_date now showing as datetime.date(...) / None instead of a raw string.
• The empty-release_date case is already exercised by the existing search_1.json/search_2.json fixtures (e.g. "Frosty"), so no new fixture was needed — reverting the deserializer causes those existing tests to fail with ValueError: Invalid isoformat string: '', not just a snapshot mismatch.
• Full suite, ruff, pylint, and mypy all pass locally.