feat(integration): 完善外部 API 對接邏輯與安全性

1. 新增 API Rate Limiting (每分鐘 60 次)
2. 實作 ProductServiceInterface 與 findOrCreateWarehouseByName 解決跨模組耦合問題
3. 強化 OrderSync API 驗證 (price 欄位限制最小 0、payment_method 加上允許白名單)
4. 實作 OrderSync API 冪等性處理，重複訂單直接回傳現有資訊
5. 修正 ProductSync API 同步邏輯，每次同步皆會更新產品分類與單位
6. 完善 integration API 對接手冊內容與 UI 排版

app/Modules/Inventory/InventoryServiceProvider.php

@@ -4,13 +4,16 @@ namespace App\Modules\Inventory;
 
 use Illuminate\Support\ServiceProvider;
 use App\Modules\Inventory\Contracts\InventoryServiceInterface;
+use App\Modules\Inventory\Contracts\ProductServiceInterface;
 use App\Modules\Inventory\Services\InventoryService;
+use App\Modules\Inventory\Services\ProductService;
 
 class InventoryServiceProvider extends ServiceProvider
 {
     public function register(): void
     {
         $this->app->bind(InventoryServiceInterface::class, InventoryService::class);
+        $this->app->bind(ProductServiceInterface::class, ProductService::class);
     }
 
     public function boot(): void