feat(plex): person cards in the grid for the filtered actors (S3)

The actors currently in the filter now render as cards above the poster grid —
headshot + name + in-scope title count + a remove x — so you SEE who you're
exploring, not just chips in the rail (generalises the old search-only person
cards to the applied filter). New GET /plex/people/cards (photo from the
plex_people cache, count live against cast_names); PlexBrowse fetches + renders
them; i18n en/hu. Verified: John Goodman (11) / Douglas M. Griffin (1) / Bradley
Cooper (14) with photos + counts. (Plex cast-explore S3)

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

@@ -225,5 +225,10 @@
     "addShow": "Add whole show to a playlist",
     "addSeason": "Add season to a playlist",
     "addEpisode": "Add episode to a playlist"
+  },
+  "people": {
+    "count_one": "{{count}} title",
+    "count_other": "{{count}} titles",
+    "remove": "Remove from filter"
   }
-}
+}

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

@@ -225,5 +225,10 @@
     "addShow": "Egész sorozat listához adása",
     "addSeason": "Évad listához adása",
     "addEpisode": "Epizód listához adása"
+  },
+  "people": {
+    "count_one": "{{count}} cím",
+    "count_other": "{{count}} cím",
+    "remove": "Eltávolítás a szűrőből"
   }
-}
+}