feat: enhance error handling and validation infrastructure
- Add comprehensive Zod error helper with German localization
- Migrate from deprecated .toPromise() to firstValueFrom()
- Enhance global error handler with ZodError support
- Implement storage features for signal stores with auto-save
- Add comprehensive test coverage for validation scenarios
- Update multiple stores with improved storage integration
- Extend tab management with enhanced navigation patterns
- Add checkout data-access barrel exports
- Update core-storage documentation with usage examples
Major improvements:
- Complete German error message translations for all Zod validation types
- Auto-save with configurable debouncing for signal stores
- Type-safe storage integration with schema validation
- Enhanced entity management with orphan cleanup
- Robust fallback strategies for validation failures
Breaking: Requires Zod validation errors to use new helper
Refs: #5345#5353
Related work items: #5345, #5353
refactor(checkout): migrate purchase options to shopping cart-based architecture
Replace processId with shoppingCartId in purchase options modal and related components
Add new checkout data-access library with facades, services, and schemas
Update PurchaseOptionsService to use new checkout facade pattern
Migrate state management from process-based to shopping cart-based approach
Update selectors and store to handle shoppingCartId instead of processId
Improve type safety with Zod schemas for checkout operations
Add proper error handling and logging throughout checkout services
Update article details and checkout review components to use new patterns
BREAKING CHANGE: Purchase options modal now requires shoppingCartId instead of processId
Related work items: #5350
