E5 S5: enriched Plex detail page (ratings + facts + keywords + crew)

Consumes the TMDB block the S2 engine already persists + serves (movie/show
detail's `tmdb`), turning the movie info page into a Seerr-style enriched detail
(page variant only — the player overlay stays lean):

- Multi-source ratings row: IMDb (links out) · TMDb (with vote count) · Plex
  audience — whichever are present. Only the primary score (IMDb, else audience)
  carries the ratingMin filter, mirroring the backend rating column.
- Facts panel: release · runtime · cert · budget · revenue · studios · countries.
- Keyword chips → tap to filter the library. Backend: a new `keywords` filter on
  LibraryFilters + meta_filter_conds (`keywords @> [kw]`, both models), wired
  through PlexFilters (appendPlexFilters / plexFilterCount / active-chip / clear).
- Full crew (TMDB key-crew) → tap a name to open their person page.

Tests: test_plex_keyword_filter.py (3) + PlexInfo.dom.test.tsx (5, incl. the
overlay-stays-lean guard). New i18n plex.info.facts.* / keywords / crew / audience
(en+hu). Gate: vitest 337, backend lane 396.

frontend/src/i18n/locales/en/plex.json

@@ -204,7 +204,21 @@
     "filterRating": "Show titles rated {{n}}+",
     "filterActor": "Show titles with {{name}}",
     "viewPerson": "View {{name}}'s filmography",
-    "browseCollection": "Browse collection →"
+    "browseCollection": "Browse collection →",
+    "audience": "Audience",
+    "keywords": "Keywords",
+    "crew": "Crew",
+    "filterKeyword": "Filter by \"{{name}}\"",
+    "facts": {
+      "title": "Details",
+      "release": "Released",
+      "runtime": "Runtime",
+      "cert": "Rating",
+      "budget": "Budget",
+      "revenue": "Revenue",
+      "studios": "Studios",
+      "countries": "Countries"
+    }
   },
   "playable": {
     "direct": "Plays directly in the browser",

frontend/src/i18n/locales/hu/plex.json

@@ -204,7 +204,21 @@
     "filterRating": "{{n}}+ pontos címek",
     "filterActor": "Címek {{name}} szereplésével",
     "viewPerson": "{{name}} filmográfiája",
-    "browseCollection": "Kollekció böngészése →"
+    "browseCollection": "Kollekció böngészése →",
+    "audience": "Közönség",
+    "keywords": "Kulcsszavak",
+    "crew": "Stáb",
+    "filterKeyword": "Szűrés erre: „{{name}}”",
+    "facts": {
+      "title": "Részletek",
+      "release": "Megjelenés",
+      "runtime": "Hossz",
+      "cert": "Korhatár",
+      "budget": "Költségvetés",
+      "revenue": "Bevétel",
+      "studios": "Stúdiók",
+      "countries": "Országok"
+    }
   },
   "playable": {
     "direct": "Közvetlenül játszható a böngészőben",