Feature: Add 24-hour cleanup for incomplete orders and update status display

- Create cleanupOrders utility to delete pending orders older than 24 hours
- Update admin notifications to only count recent pending orders (< 24h old)
- Automatically call cleanup when customer initiates checkout
- Change status display from "PENDING" to "Waiting payment" for customer-facing views
- Update both customer account page and admin orders page with new status label
- Incomplete orders automatically purged, reducing admin clutter

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

src/app/api/checkout/route.ts

@@ -6,6 +6,7 @@ import { getEffectivePrice } from '@/lib/pricing';
 import { fetchActivePromotions } from '@/lib/promotions';
 import { checkRateLimit, getClientIp } from '@/lib/rateLimit';
 import { getRoyalMailShippingQuotes } from '@/lib/royalmail-shipping';
+import { cleanupPendingOrders } from '@/lib/cleanupOrders';
 
 type CheckoutCartItem = {
   productId: string;
@@ -51,6 +52,9 @@ export async function POST(req: Request) {
       );
     }
 
+    // Clean up old incomplete orders (non-blocking)
+    cleanupPendingOrders().catch((err) => console.error('Cleanup error:', err));
+
     const body = await req.json();
     console.log('Checkout request received with items:', body.items?.length, 'customerId:', body.customerId);
     const items: CheckoutCartItem[] = body.items ?? [];