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]>

resources/views/user/channel.blade.php

@@ -1843,7 +1843,13 @@ $headerSocialMap = [
     @if($playlists && $playlists->count() > 0)
     <div class="ch-playlists-grid">
         @foreach($playlists as $playlist)
-        <a href="{{ route('playlists.show', $playlist->id) }}" class="ch-playlist-card">
+        @php
+            $plFirstVid = $playlist->videos->first();
+            $plCardUrl  = $plFirstVid
+                ? route('videos.show', $plFirstVid) . '?playlist=' . $playlist->share_token
+                : route('playlists.show', $playlist->id);
+        @endphp
+        <a href="{{ $plCardUrl }}" class="ch-playlist-card">
             <div class="ch-playlist-thumb">
                 @if($playlist->thumbnail_url)
                     <img src="{{ $playlist->thumbnail_url }}" alt="{{ $playlist->name }}" loading="lazy">