refactor(inventory): 重構倉庫管理邏輯，移除 is_sellable 欄位並改由類型判定可用庫存

app/Modules/Inventory/Models/Warehouse.php

@@ -18,13 +18,11 @@ class Warehouse extends Model
         'type',
         'address',
         'description',
-        'is_sellable',
         'license_plate',
         'driver_name',
     ];
 
     protected $casts = [
-        'is_sellable' => 'boolean',
         'type' => \App\Enums\WarehouseType::class,
     ];