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]>

tests/unit/test_normalizer.py

@@ -156,7 +156,9 @@ def test_normalize_movie_maps_genres_and_keywords():
     movie = normalize_movie(FAKE_MOVIE)
     assert movie.genres == ["Action", "Science Fiction"]
     assert movie.keywords == ["dystopia"]
-    assert movie.alternate_titles == ["Matrix"]
+    assert len(movie.alternate_titles) == 1
+    assert movie.alternate_titles[0].title == "Matrix"
+    assert movie.alternate_titles[0].country_code == "US"
 
 
 def test_normalize_movie_maps_cast_and_crew():
@@ -225,6 +227,21 @@ def test_normalize_movie_maps_collection_and_recommendations():
     assert movie.recommendation_external_ids == ["604"]
 
 
+def test_normalize_movie_alternate_titles_capture_type_and_skip_titleless_entries():
+    with_type = {
+        **FAKE_MOVIE,
+        "alternative_titles": {
+            "titles": [
+                {"title": "Matrix", "iso_3166_1": "US", "type": "working title"},
+                {"iso_3166_1": "FR"},  # no "title" key at all -- must be skipped
+            ]
+        },
+    }
+    movie = normalize_movie(with_type)
+    assert len(movie.alternate_titles) == 1
+    assert movie.alternate_titles[0].type == "working title"
+
+
 def test_normalize_movie_maps_release_dates_and_certification():
     movie = normalize_movie(FAKE_MOVIE)
     assert len(movie.release_dates) == 4
@@ -431,7 +448,9 @@ def test_normalize_series_keywords_and_alt_titles_use_tv_shaped_keys():
     # for /movie — a normalizer bug here would silently return empty lists.
     series = normalize_series(FAKE_SERIES)
     assert series.keywords == ["drug dealer"]
-    assert series.alternate_titles == ["Breaking Bad"]
+    assert len(series.alternate_titles) == 1
+    assert series.alternate_titles[0].title == "Breaking Bad"
+    assert series.alternate_titles[0].country_code == "US"
 
 
 def test_normalize_series_keeps_season_zero_specials():