[FEAT] 實作機台廣告管理模組與多語系支援

1. 新增廣告管理列表與機台配置介面，包含多語系 (zh_TW, en, ja) 與完整 CRUD
2. 實作基於 Alpine 的廣告素材預覽輪播功能
3. 優化廣告素材下拉選單，強制綁定所屬公司以達成多租戶資料隔離
4. 重構廣告配置中廣告影片的縮圖渲染邏輯，移除 <video> 標籤以大幅提升頁面載入速度與節省頻寬
5. 放寬個人檔案頭像上傳限制，支援 WebP 格式

app/Models/Machine/MachineAdvertisement.php

@@ -0,0 +1,43 @@
+<?php
+
+namespace App\Models\Machine;
+
+use App\Models\System\Advertisement;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+
+class MachineAdvertisement extends Model
+{
+    use HasFactory;
+
+    protected $fillable = [
+        'machine_id',
+        'advertisement_id',
+        'position',
+        'sort_order',
+        'start_at',
+        'end_at',
+    ];
+
+    protected $casts = [
+        'sort_order' => 'integer',
+        'start_at' => 'datetime',
+        'end_at' => 'datetime',
+    ];
+
+    /**
+     * Get the advertisement associated with this assignment.
+     */
+    public function advertisement()
+    {
+        return $this->belongsTo(Advertisement::class);
+    }
+
+    /**
+     * Get the machine associated with this assignment.
+     */
+    public function machine()
+    {
+        return $this->belongsTo(Machine::class);
+    }
+}