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>

assets/css/admin.css

@@ -598,12 +598,36 @@
 	display: inline-block;
 	padding: 3px 8px;
 	border-radius: 3px;
-	color: #fff;
 	font-size: 12px;
 	font-weight: 600;
 	text-transform: uppercase;
 }
 
+.bnb-status-pending {
+	background: #fff8e5;
+	color: #9d6a00;
+}
+
+.bnb-status-confirmed {
+	background: #e6f4ea;
+	color: #0a6e31;
+}
+
+.bnb-status-checked_in {
+	background: #e3f2fd;
+	color: #1565c0;
+}
+
+.bnb-status-checked_out {
+	background: #f5f5f5;
+	color: #616161;
+}
+
+.bnb-status-cancelled {
+	background: #ffeaea;
+	color: #d63638;
+}
+
 /* Room Details Meta Box */
 #bnb_room_details .form-table td label {
 	display: inline-block;