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.

frontend/src/lib/api/plex.ts

@@ -211,6 +211,15 @@ export interface PlexPersonCard {
 export interface PlexPersonDetail {
   name: string;
   photo?: string | null; // cached headshot, or null (placeholder)
+  // TMDB bio (E5 S6), lazily fetched on first open, then served from the row. Null when the person has
+  // no linked tmdb_person_id (never appeared in a TMDB-enriched title) or TMDB has no data.
+  biography?: string | null;
+  birthday?: string | null; // "YYYY-MM-DD"
+  deathday?: string | null;
+  place_of_birth?: string | null;
+  known_for_department?: string | null;
+  also_known_as: string[];
+  known_for: PlexCard[]; // their most-popular credits that are IN our library (deep-linkable)
   movies: PlexCard[]; // enabled-library movies whose cast OR directors include this person
   shows: PlexCard[]; // enabled-library shows, same
 }