Added Deutsche Post as a shipping carrier, including new models, admin, serializers, and API client integration. Updated Carrier and SiteConfiguration models to support Deutsche Post, including shipping price and API credentials. Added requirements for the Deutsche Post API client and dependencies.
Refactored order creation logic to use new serializers and transaction handling, improving validation and modularity. Introduced admin and public endpoints for shop configuration with sensitive fields protected. Enhanced Zásilkovna (Packeta) integration, including packet widget template, new API fields, and improved error handling. Added django-silk for profiling, updated requirements and settings, and improved frontend Orval config for API client generation.
