feat(notification): 實作通知輪詢與優化顯示名稱

- 新增通知輪詢 API 與前端自動更新機制
- 修正生產工單單號格式為 PRO-YYYYMMDD-XX
- 確保通知顯示實際建立者名稱而非系統

app/Modules/Procurement/Observers/PurchaseOrderObserver.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace App\Modules\Procurement\Observers;
+
+use App\Modules\Procurement\Models\PurchaseOrder;
+use App\Modules\Procurement\Notifications\NewPurchaseOrder;
+use App\Modules\Core\Models\User;
+use Illuminate\Support\Facades\Notification;
+
+class PurchaseOrderObserver
+{
+    /**
+     * Handle the PurchaseOrder "created" event.
+     */
+    public function created(PurchaseOrder $purchaseOrder): void
+    {
+        // 找出有檢視採購單權限的使用者
+        $users = User::permission('purchase_orders.view')->get();
+        
+        // 排除建立者自己（避免自己收到自己的通知）
+        // $users = $users->reject(function ($user) use ($purchaseOrder) {
+        //     return $user->id === $purchaseOrder->user_id;
+        // });
+
+        $creatorName = $purchaseOrder->user ? $purchaseOrder->user->name : '系統';
+
+        if ($users->isNotEmpty()) {
+            Notification::send($users, new NewPurchaseOrder($purchaseOrder, $creatorName));
+        }
+    }
+}