Add multi-language audio tracks and self-hosted flag-icons

Introduce per-video language support and multiple audio tracks
(VideoAudioTrack model + migrations for language, description, title),
a reusable language-select component, and a track-editor form. Bundle
the self-hosted flag-icons v7.2.3 library and a NAS auto-sync command.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

app/Http/Controllers/SuperAdminController.php

@@ -1305,6 +1305,7 @@ class SuperAdminController extends Controller
             }
             \DB::table('users')->update(['avatar' => null, 'banner' => null]);
             Setting::set('nas_sync_enabled', 'false');
+            app(\App\Services\NasSyncService::class)->flushReachabilityCache();
             AuditLog::record('admin.nas_disabled_fresh');
             return response()->json(['ok' => true]);
         }