feat(plex): expanded metadata filters, clickable info page, image disk cache

Backend (migration 0045_plex_filter_meta): plex_items gains rating (audienceRating
~IMDb), content_rating, studio, originally_available_at, and GIN-indexed genres /
directors / cast_names — all mirrored from the cheap section listing (no per-item API
calls; they also seed a future watch-habit recommender). /browse gains genre / content-
rating / year / rating / duration / added-within / director / actor / studio filters
(@> containment, GIN) + sort by year|rating|duration|release; new /facets endpoint
returns available genres+ratings (with counts) and the year/rating/duration bounds. A
thin on-disk image cache (.plex-img-cache) serves posters/art/cast photos from local
disk after first fetch (~7-14x faster repeat loads).

Frontend: PlexSidebar grows the full filter set (facet-driven genre/age chips, rating
steps, year range inputs, duration buckets, added-within, active people/studio chips,
clear-all); filters persist per-account as one JSON blob. PlexInfo metadata (year,
genre, director, cast, studio, IMDb score) is clickable → sets the matching filter and
returns to the filtered grid (page variant only; the in-player overlay stays read-only
so a stray click can't stop playback). i18n en/hu/de.

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

@@ -5,7 +5,11 @@
   "searchPlaceholder": "Keresés a Plexben…",
   "sort": {
     "added": "Nemrég hozzáadott",
-    "title": "Cím"
+    "title": "Cím",
+    "year": "Év",
+    "rating": "IMDb pont",
+    "duration": "Hossz",
+    "release": "Megjelenés dátuma"
   },
   "filter": {
     "library": "Könyvtár",
@@ -16,7 +20,18 @@
       "in_progress": "Folyamatban",
       "watched": "Megnézett"
     },
-    "sort": "Rendezés"
+    "sort": "Rendezés",
+    "clearAll": "Szűrők törlése",
+    "active": "Aktív",
+    "any": "Bármi",
+    "rating": "IMDb pont",
+    "genre": "Műfaj",
+    "year": "Év",
+    "duration": "Hossz",
+    "durationOpt": { "short": "90 perc alatt", "mid": "90–120 perc", "long": "2 óra felett" },
+    "added": "Plexhez adva",
+    "addedOpt": { "24h": "24 óra", "1w": "1 hét", "1m": "1 hónap", "6m": "6 hónap", "1y": "1 év" },
+    "contentRating": "Korhatár"
   },
   "count": "{{count}} cím",
   "searchCount": "{{count}} találat",
@@ -76,7 +91,10 @@
     "cast": "Szereplők & stáb",
     "markWatched": "Megjelölés megnézettként",
     "markUnwatched": "Megnézett visszavonása",
-    "clearResume": "Folytatási pozíció törlése"
+    "clearResume": "Folytatási pozíció törlése",
+    "filterYear": "{{year}} évi címek",
+    "filterRating": "{{n}}+ pontos címek",
+    "filterActor": "Címek {{name}} szereplésével"
   },
   "playable": {
     "direct": "Közvetlenül játszható a böngészőben",