Add keyword browsing/filtering and expose alternate titles

Keywords were ingested and shown read-only on detail pages, but had no
directory (GET /keywords) or filter param -- the same gap genres had
before today. Mirrors the genre browse pattern exactly: repository,
service, route, plus a `keyword` filter on GET /movies and GET /series.

Alternate/translated titles ("Also Known As") were normalized down to
bare title strings and never written to MovieAlternateTitle/
SeriesAlternateTitle at all. Normalizer now captures country_code + type
per TMDb's actual shape; ingestion writes them; movie/series detail now
expose an alternate_titles list.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

app/schemas/movie.py

@@ -7,6 +7,7 @@ from datetime import date, datetime
 from pydantic import BaseModel
 
 from app.schemas.common import (
+    AlternateTitleOut,
     CastCreditOut,
     CollectionBriefOut,
     CompanyBriefOut,
@@ -57,6 +58,7 @@ class MovieDetailOut(BaseModel):
 
     genres: list[GenreOut] = []
     keywords: list[KeywordOut] = []
+    alternate_titles: list[AlternateTitleOut] = []
     cast: list[CastCreditOut] = []
     crew: list[CrewCreditOut] = []
     companies: list[CompanyBriefOut] = []