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/main.py

@@ -28,6 +28,7 @@ from app.api.v1 import (
     episodes,
     genres,
     health,
+    keywords,
     movies,
     people,
     search,
@@ -177,4 +178,5 @@ app.include_router(people.router, prefix=API_V1_PREFIX)
 app.include_router(collections.router, prefix=API_V1_PREFIX)
 app.include_router(companies.router, prefix=API_V1_PREFIX)
 app.include_router(genres.router, prefix=API_V1_PREFIX)
+app.include_router(keywords.router, prefix=API_V1_PREFIX)
 app.include_router(admin.router, prefix=API_V1_PREFIX)