feat(checkout): add branch selection to reward catalog
- Add new select-branch-dropdown library with BranchDropdownComponent
and SelectedBranchDropdownComponent for branch selection
- Extend DropdownButtonComponent with filter and option subcomponents
- Integrate branch selection into reward catalog page
- Add BranchesResource for fetching available branches
- Update CheckoutMetadataService with branch selection persistence
- Add comprehensive tests for dropdown components
Related work items: #5464
- Add new reward-order-confirmation feature library with components and store
- Implement checkout completion orchestrator service for order finalization
- Migrate checkout/oms/crm models to Zod schemas for better type safety
- Add order creation facade and display order schemas
- Update shopping cart facade with order completion flow
- Add comprehensive tests for shopping cart facade
- Update routing to include order confirmation page
