新增 POS 庫存查詢 API：實作 InventorySyncController 與相關 Service 邏輯，並更新 API 整合手冊

app/Modules/Integration/Controllers/InventorySyncController.php

@@ -0,0 +1,51 @@
+<?php
+
+namespace App\Modules\Integration\Controllers;
+
+use App\Http\Controllers\Controller;
+use App\Modules\Inventory\Contracts\InventoryServiceInterface;
+use Illuminate\Http\JsonResponse;
+
+class InventorySyncController extends Controller
+{
+    protected $inventoryService;
+
+    public function __construct(InventoryServiceInterface $inventoryService)
+    {
+        $this->inventoryService = $inventoryService;
+    }
+
+    /**
+     * 提供外部 POS 查詢指定倉庫的商品庫存餘額
+     *
+     * @param string $warehouseCode
+     * @return JsonResponse
+     */
+    public function show(string $warehouseCode): JsonResponse
+    {
+        // 透過 Service 調用跨模組庫存查詢功能
+        $inventoryData = $this->inventoryService->getPosInventoryByWarehouseCode($warehouseCode);
+
+        // 若回傳 null，表示尋無此倉庫代碼
+        if (is_null($inventoryData)) {
+            return response()->json([
+                'status' => 'error',
+                'message' => "Warehouse with code '{$warehouseCode}' not found.",
+            ], 404);
+        }
+
+        // 以 JSON 格式回傳組合好的商品庫存列表
+        return response()->json([
+            'status' => 'success',
+            'warehouse_code' => $warehouseCode,
+            'data' => $inventoryData->map(function ($item) {
+                return [
+                    'external_pos_id' => $item->external_pos_id,
+                    'product_code' => $item->product_code,
+                    'product_name' => $item->product_name,
+                    'quantity' => (float) $item->total_quantity,
+                ];
+            })
+        ], 200);
+    }
+}