- Add ShippingRate model to Prisma schema with service name, base price, per-kg surcharge, estimated delivery days, and international flag
- Create migration to add shipping_rates table
- Update seed.ts to populate initial Royal Mail rates (domestic and international)
- Refactor getRoyalMailShippingQuotes to fetch rates from database with fallback to defaults
- Add /admin/shipping-rates page for managing rates
- Add ShippingRatesForm component with inline editing and add/remove functionality
- Add server actions for saving and deleting rates
- Add "Shipping rates" link to admin navigation
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
