E5 S6: enriched person page (TMDB bio + birth facts + Known-for rail)

The person page now leads with a TMDB bio, lazily fetched the first time it's
opened (off the S2-linked `tmdb_person_id`) and then served from the row:

- Migration 0072: ADD-only nullable person columns on plex_people — biography,
  birthday, deathday, place_of_birth, known_for_department, also_known_as,
  known_for ([{tmdb_id, media_type, title}]), tmdb_enriched_at.
- tmdb.py: TmdbClient.fetch_person (/person/{id}+combined_credits), parse_person
  (bio + a popularity-ranked, deduped known_for), apply_person, enrich_person
  (lazy one-shot, key+id guarded, commits, 404 stamps the watermark).
- people.py person_detail: loads the full person row, lazily enriches (best-effort
  — never fails the page), serves the bio fields + resolves known_for to library
  rows by guid (in-library only, popularity order).
- FE PlexPersonView: bio/birth-facts/aka hero + a "Known for" Carousel rail above
  the existing Movies/Shows filmography; PlexPersonDetail type + i18n (en+hu).

Tests: test_plex_person_bio.py (6: parse / lazy-enrich guards / serve) + extended
PlexPersonView.dom.test.tsx + the unknown-name contract in test_plex_person.py.
Browser-E2E'd on Jim Carrey (live TMDB enrich → bio 1937 chars, born 1962-01-17
Newmarket, Known-for resolved). Gate: vitest 337, backend lane 402.

backend/tests/test_plex_person.py

@@ -100,7 +100,20 @@ def test_person_detail_unknown_name_is_empty(db, monkeypatch):
     resp = _get(db, user, monkeypatch, "/api/plex/person/Ghost%20Actor")
     assert resp.status_code == 200, resp.text
     body = resp.json()
-    assert body == {"name": "Ghost Actor", "photo": None, "movies": [], "shows": []}
+    # An unknown name has no plex_people row → no bio, no titles (E5 S6 added the bio fields, all null).
+    assert body == {
+        "name": "Ghost Actor",
+        "photo": None,
+        "biography": None,
+        "birthday": None,
+        "deathday": None,
+        "place_of_birth": None,
+        "known_for_department": None,
+        "also_known_as": [],
+        "known_for": [],
+        "movies": [],
+        "shows": [],
+    }
 
 
 def test_content_libs_partitions_only_enabled(db):