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>

admin/functions.php

@@ -9,7 +9,7 @@ function formipay_field_type_collection() {
         'number' => __( 'Number', 'formipay' ), 
         'date' => __( 'Date', 'formipay' ), 
         'datetime' => __( 'Date & Time', 'formipay' ), 
-        'color' => __( 'Number', 'formipay' ),
+        'color' => __( 'Color', 'formipay' ),
         'select' => __( 'Select Dropdown', 'formipay' ), 
         'checkbox' => __( 'Checkbox', 'formipay' ), 
         'radio' => __( 'Radio', 'formipay' ),