Update codebase

backend/food/merchant_ops/preparing.php

@@ -0,0 +1,11 @@
+<?php
+// food/merchant_ops/preparing.php — المطعم بدأ التحضير
+require_once __DIR__ . '/../connect_merchant.php';
+
+$orderId = filterRequest('order_id', 'int');
+if (!$orderId) jsonError('order_id is required');
+
+foodAssertOrderOwnership($orderId, 'merchant', (string)$food_merchant_id);
+food_transition_status($orderId, 'preparing', 'merchant', (string)$food_merchant_user_id);
+
+jsonSuccess(['order_id' => $orderId, 'status' => 'preparing']);