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/serializers.py

@@ -0,0 +1,38 @@
+from rest_framework import serializers
+
+from .models import ZasilkovnaPacket, ZasilkovnaShipment
+
+
+class ZasilkovnaPacketSerializer(serializers.ModelSerializer):
+	class Meta:
+		model = ZasilkovnaPacket
+		fields = [
+			"id",
+			"created_at",
+			"packet_id",
+			"barcode",
+			"state",
+			"weight",
+			"return_routing",
+		]
+		read_only_fields = fields
+
+
+class TrackingURLSerializer(serializers.Serializer):
+	barcode = serializers.CharField(read_only=True)
+	tracking_url = serializers.URLField(read_only=True)
+
+
+class ZasilkovnaShipmentSerializer(serializers.ModelSerializer):
+	packets = serializers.PrimaryKeyRelatedField(many=True, read_only=True)
+
+	class Meta:
+		model = ZasilkovnaShipment
+		fields = [
+			"id",
+			"created_at",
+			"shipment_id",
+			"barcode",
+			"packets",
+		]
+		read_only_fields = fields