feat: 實作 POS API 整合功能，包含商品與銷售訂單同步及韌性機制

app/Modules/Integration/Controllers/ProductSyncController.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace App\Modules\Integration\Controllers;
+
+use App\Http\Controllers\Controller;
+use Illuminate\Http\Request;
+use App\Modules\Inventory\Services\ProductService;
+use Illuminate\Support\Facades\Log;
+
+class ProductSyncController extends Controller
+{
+    protected $productService;
+
+    public function __construct(ProductService $productService)
+    {
+        $this->productService = $productService;
+    }
+
+    public function upsert(Request $request)
+    {
+        $request->validate([
+            'external_pos_id' => 'required|string',
+            'name' => 'required|string',
+            'price' => 'nullable|numeric',
+            'sku' => 'nullable|string',
+            'barcode' => 'nullable|string',
+            'category' => 'nullable|string',
+            'unit' => 'nullable|string',
+            'updated_at' => 'nullable|date',
+        ]);
+
+        try {
+            $product = $this->productService->upsertFromPos($request->all());
+
+            return response()->json([
+                'message' => 'Product synced successfully',
+                'data' => [
+                    'id' => $product->id,
+                    'external_pos_id' => $product->external_pos_id,
+                ]
+            ]);
+        } catch (\Exception $e) {
+            Log::error('Product Sync Failed', ['error' => $e->getMessage(), 'payload' => $request->all()]);
+            return response()->json(['message' => 'Sync failed'], 500);
+        }
+    }
+}