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/app/plex/tmdb.py

@@ -119,6 +119,10 @@ class TmdbClient:
         """Resolve an external id (imdb_id / tvdb_id) to TMDB items via /find."""
         return self._get(f"/find/{external_id}", {"external_source": source})
 
+    def fetch_person(self, person_id: int) -> dict | None:
+        """One person's bio + combined credits (E5 S6), in a single append_to_response request."""
+        return self._get(f"/person/{person_id}", {"append_to_response": "combined_credits"})
+
 
 def guid_to_tmdb_id(guid: str | None, media_type: str, tmdb: TmdbClient) -> int | None:
     """Map a stored canonical guid to a TMDB id. `tmdb:` is direct; `imdb:`/`tvdb:` go through /find
@@ -377,3 +381,67 @@ def serve_block(db: Session, row) -> dict | None:
         "recommendations": resolve_recs(db, row.recommendations),
         "backdrops": row.backdrops or [],
     }
+
+
+# --- Person enrichment (E5 S6) -------------------------------------------------------------------
+# A person's bio + birth facts + a "Known for" credit pool, fetched once (the first person-page open)
+# and served from the plex_people row. `known_for` stores the top combined-credits ids; the person
+# endpoint resolves them to library rows by guid at serve time (like recommendations).
+
+_KNOWN_FOR_MAX = 15
+
+
+def parse_person(payload: dict) -> dict:
+    """TMDB /person/{id} (+combined_credits) → the persisted bio fields. `known_for` = the person's
+    most-popular movie/tv credits (deduped by id), top `_KNOWN_FOR_MAX`, resolved to library later."""
+    credits = (payload.get("combined_credits") or {}).get("cast") or []
+    seen: set[int] = set()
+    known: list[dict] = []
+    for c in sorted(credits, key=lambda c: c.get("popularity") or 0, reverse=True):
+        tid, mt = c.get("id"), c.get("media_type")
+        if not tid or mt not in ("movie", "tv") or tid in seen:
+            continue
+        seen.add(tid)
+        known.append({"tmdb_id": tid, "media_type": mt, "title": c.get("title") or c.get("name")})
+        if len(known) >= _KNOWN_FOR_MAX:
+            break
+    return {
+        "biography": (payload.get("biography") or "").strip() or None,
+        "birthday": payload.get("birthday") or None,
+        "deathday": payload.get("deathday") or None,
+        "place_of_birth": payload.get("place_of_birth") or None,
+        "known_for_department": payload.get("known_for_department") or None,
+        "also_known_as": payload.get("also_known_as") or None,
+        "known_for": known or None,
+    }
+
+
+def apply_person(row: PlexPerson, parsed: dict) -> None:
+    row.biography = parsed["biography"]
+    row.birthday = parsed["birthday"]
+    row.deathday = parsed["deathday"]
+    row.place_of_birth = parsed["place_of_birth"]
+    row.known_for_department = parsed["known_for_department"]
+    row.also_known_as = parsed["also_known_as"]
+    row.known_for = parsed["known_for"]
+    row.tmdb_enriched_at = datetime.now(timezone.utc)
+
+
+def enrich_person(db: Session, person: PlexPerson) -> bool:
+    """Lazily fetch + persist one person's TMDB bio (first person-page open), committing the write so it
+    survives regardless of the read path. No-op (False) without a key or a `tmdb_person_id`; a transient
+    error leaves `tmdb_enriched_at` NULL so the next open retries. A 404 (deleted person) stamps the
+    watermark with empty fields so we don't refetch it every open."""
+    if not person.tmdb_person_id or not sysconfig.get_str(db, "tmdb_api_key"):
+        return False
+    try:
+        with TmdbClient(db) as tmdb:
+            payload = tmdb.fetch_person(person.tmdb_person_id)
+    except TmdbError:
+        return False
+    if payload is None:
+        person.tmdb_enriched_at = datetime.now(timezone.utc)
+    else:
+        apply_person(person, parse_person(payload))
+    db.commit()
+    return True