Add WooCommerce integration for payments, invoices, and order management (v0.11.0)

- Product sync: Virtual WC products for rooms with bidirectional linking
- Cart/Checkout: Booking data in cart items, availability validation, dynamic pricing
- Orders: Automatic booking creation on payment, status mapping, guest record creation
- Invoices: PDF generation via mPDF, auto-attach to emails, configurable numbering
- Refunds: Full refund cancels booking, partial refund records amount only
- Admin: Cross-linked columns and row actions between bookings and orders
- Settings: WooCommerce tab with subtabs (General, Products, Orders, Invoices)
- HPOS compatibility declared for High-Performance Order Storage

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

wp-bnb.php

@@ -3,7 +3,7 @@
  * Plugin Name: WP BnB Management
  * Plugin URI: https://src.bundespruefstelle.ch/magdev/wp-bnb
  * Description: A comprehensive Bed & Breakfast management system for WordPress. Manage buildings, rooms, bookings, and guests.
- * Version: 0.10.1
+ * Version: 0.11.0
  * Requires at least: 6.0
  * Requires PHP: 8.3
  * Author: Marco Graetsch
@@ -24,7 +24,7 @@ if ( ! defined( 'ABSPATH' ) ) {
 }
 
 // Plugin version constant - MUST match Version in header above.
-define( 'WP_BNB_VERSION', '0.10.1' );
+define( 'WP_BNB_VERSION', '0.11.0' );
 
 // Plugin path constants.
 define( 'WP_BNB_PATH', plugin_dir_path( __FILE__ ) );