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/Models/VideoAudioTrack.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class VideoAudioTrack extends Model
+{
+    protected $fillable = ['video_id', 'language', 'label', 'title', 'description', 'path', 'filename'];
+
+    public function video(): BelongsTo
+    {
+        return $this->belongsTo(Video::class);
+    }
+
+    public function getStreamUrlAttribute(): string
+    {
+        return route('videos.audio-track', ['video' => $this->video_id, 'track' => $this->id]);
+    }
+
+    /** Absolute local path to the file, regardless of NAS or local storage. */
+    public function localPath(): string
+    {
+        return storage_path('app/' . $this->path);
+    }
+}