Add Jellyfin mappings and optimize cast queries

Performance and settings updates:

- Add a new jellyfin_library_mappings column to the settings table and wire it into the Settings model (update handling and default value). This enables storing Jellyfin library mappings in settings.
- Optimize Cast::list by loading all cast filmography in a single joined query and grouping results per cast to avoid N+1 queries.
- Remove per-item cast/staff loading in Media model to avoid repeated queries during list/search operations.
- Remove game-specific enrichment from MediaController search to stop extra game info lookups during search responses.

These changes reduce repeated DB calls and centralize Jellyfin mapping storage.

api/controllers/MediaController.php

@@ -278,17 +278,7 @@ class MediaController {
         $limit = isset($_GET['limit']) ? (int)$_GET['limit'] : 20;
         
         $result = $this->media->search($filters, $page, $limit);
-        
-        // Game-spezifische Daten für Games laden
-        foreach ($result['items'] as &$item) {
-            if ($item['type'] === 'Game') {
-                $gameInfo = $this->game->getGameInfoForList($item['id']);
-                if ($gameInfo) {
-                    $item = array_merge($item, $gameInfo);
-                }
-            }
-        }
-        
+
         return ['success' => true, 'data' => $result];
     }