Major refactor of commerce and Stripe integration

Refactored commerce models to support refunds, invoices, and improved carrier/payment logic. Added new serializers and viewsets for products, categories, images, discount codes, and refunds. Introduced Stripe client integration and removed legacy Stripe admin/model code. Updated Dockerfile for PDF generation dependencies. Removed obsolete migration files and updated configuration app initialization. Added invoice template and tasks for order cleanup.

backend/thirdparty/zasilkovna/urls.py

@@ -0,0 +1,15 @@
+from django.urls import path, include
+from rest_framework.routers import DefaultRouter
+
+from .views import ZasilkovnaShipmentViewSet, ZasilkovnaPacketViewSet
+
+
+router = DefaultRouter()
+router.register(r"shipments", ZasilkovnaShipmentViewSet, basename="zasilkovna-shipment")
+router.register(r"packets", ZasilkovnaPacketViewSet, basename="zasilkovna-packet")
+
+app_name = "zasilkovna"
+
+urlpatterns = [
+	path("", include(router.urls)),
+]