Refactor commerce models and add configuration app

Major refactor of commerce models: restructured Carrier, Payment, and DiscountCode models, improved order total calculation, and integrated Zasilkovna and Stripe logic. Added new configuration Django app for shop settings, updated Zasilkovna and Stripe models, and fixed Zasilkovna client WSDL URL. Removed unused serializers and views in commerce, and registered new apps in settings.

backend/thirdparty/zasilkovna/views.py

@@ -0,0 +1,8 @@
+#views.py
+
+"""
+TODO:   OBJEDNAVANÍ SE VYVOLÁVA V CARRIER V COMMERCE.MODELS.PY
+        získaní labelu, 
+        info o kurýrovi, vracení balíku, 
+        vytvoření hromadné expedice
+"""