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/commerce/tasks.py

@@ -0,0 +1,10 @@
+from .models import Order
+from django.utils import timezone
+
+def delete_expired_orders():
+    expired_orders = Order.objects.filter(status=Order.STATUS_CHOICES.CANCELLED, created_at__lt=timezone.now() - timezone.timedelta(hours=24))
+    count = expired_orders.count()
+    expired_orders.delete()
+    return count
+
+