Added:
- Weight field (weightGrams) to Product model for storing item weights
- Shipping fields to Order model (shippingCost, shippingCountry, shippingService)
- Royal Mail shipping service (royalmail-shipping.ts) with:
* Domestic and international postage calculations
* Integration ready for Royal Mail API (currently uses estimated rates)
* Support for multiple shipping services
* Clear international delivery time warnings
- Shipping quotes API endpoint (/api/checkout/shipping-quotes)
- Checkout integration to calculate and include shipping cost
Weight is stored in grams, displayed to users in kilograms.
Shipping cost is calculated based on total cart weight and destination country.
