fix(plex): the recs rail's anchor and a held recommendation are named in the reader's language (E30 S1b)

Found in the S1b UAT: 'Mert megnézted: Batman Forever' kept the English title, and
the info page's TMDB recommendations kept TMDB's English titles even for titles we
hold. A held recommendation is now named as the library names it, in the reader's
language; one we lack keeps TMDB's title.

backend/tests/test_plex_tmdb.py

@@ -255,13 +255,13 @@ def test_serve_block_none_until_enriched_and_resolves_recs(db):
     db.add_all([sequel, fresh])
     db.commit()
 
-    assert tmdb.serve_block(db, fresh) is None  # not enriched yet
+    assert tmdb.serve_block(db, fresh, lang="en") is None  # not enriched yet
 
     tmdb.apply_tmdb_detail(fresh, tmdb.parse_tmdb(MOVIE_PAYLOAD, "movie"))
     fresh.tmdb_enriched_at = datetime.now(timezone.utc)
     db.commit()
 
-    block = tmdb.serve_block(db, fresh)
+    block = tmdb.serve_block(db, fresh, lang="en")
     assert block is not None
     assert block["budget"] == 6000000
     assert block["keywords"] == ["mafia", "crime family"]
@@ -409,6 +409,7 @@ def test_resolve_recs_matches_by_media_type_not_bare_id(db):
                 {"tmdb_id": 500, "title": "Movie 500", "media_type": "movie"},
                 {"tmdb_id": 900, "title": "Show 900", "media_type": "tv"},
             ],
+            lang="en",
         )
     }
     assert miss[500]["in_library"] is False and miss[500]["rating_key"] is None
@@ -423,6 +424,7 @@ def test_resolve_recs_matches_by_media_type_not_bare_id(db):
                 {"tmdb_id": 900, "media_type": "movie"},
                 {"tmdb_id": 500, "media_type": "tv"},
             ],
+            lang="en",
         )
     }
     assert hit[900]["in_library"] is True and hit[900]["rating_key"] == "m900"