feat: add trailers and extras support

Adds support for viewing and playing trailers and bonus content from Plex.

- Add getExtras() API method to fetch extras from Plex
- Add trailer/extras metadata fields (subtype, extraType, primaryExtraKey)
- Add play trailer button with film reel icon on media detail screen
- Add "Trailers & Extras" section below cast with horizontal scroll
- Support offline mode via cache fallback
- Preserve serverId/serverName for multi-server setups

lib/i18n/nl.i18n.json

@@ -274,6 +274,7 @@
   },
   "tooltips": {
     "shufflePlay": "Willekeurig afspelen",
+    "playTrailer": "Trailer afspelen",
     "markAsWatched": "Markeer als gekeken",
     "markAsUnwatched": "Markeer als ongekeken"
   },
@@ -420,6 +421,7 @@
     "playEpisode": "S${season}E${episode}",
     "overview": "Overzicht",
     "cast": "Acteurs",
+    "extras": "Trailers & Extra's",
     "seasons": "Seizoenen",
     "studio": "Studio",
     "rating": "Leeftijd",