fix: resolve all Week 1 critical bugs (F1.1–F1.9)

- Fix Customer::update() fatal error (undefined $table_name, $new_args)
- Fix Order::delete() using wrong variable $id instead of $order_id
- Fix Order::bulk_delete() using outer $order_id instead of loop $id
- Fix Email::send_email() calling non-existent class (use parent::)
- Add missing Order import in Paypal.php
- Fix BankTransfer unique_code triple DB call (call once, reuse result)
- Fix color field label showing "Number" instead of "Color"
- Add nonce verification to Customer::formipay_tabledata_customers()

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

includes/Integration/Paypal.php

@@ -2,6 +2,7 @@
 namespace Formipay\Integration;
 use Formipay\Traits\SingletonTrait;
 use Formipay\Payment\Payment;
+use Formipay\Order as Order;
 // Exit if accessed directly
 if ( ! defined( 'ABSPATH' ) ) exit;