fix: resolve PHPStan static analysis warnings

app/Models/StatUser.php

@@ -4,6 +4,18 @@ namespace App\Models;
 
 use Illuminate\Database\Eloquent\Model;
 
+/**
+ * App\Models\StatUser
+ *
+ * @property int $id
+ * @property int $user_id 用户ID
+ * @property int $u 上行流量
+ * @property int $d 下行流量
+ * @property int $record_at 记录时间
+ * @property int $created_at
+ * @property int $updated_at
+ * @property-read int $value 通过SUM(u + d)计算的总流量值，仅在查询指定时可用
+ */
 class StatUser extends Model
 {
     protected $table = 'v2_stat_user';