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/urls.py

@@ -1,15 +1,24 @@
 from django.urls import path, include
 from rest_framework.routers import DefaultRouter
-from .views import CategoryViewSet, ProductViewSet, DiscountCodeViewSet, OrderViewSet
+from .views import (
+    OrderViewSet,
+    ProductViewSet,
+    CategoryViewSet,
+    ProductImageViewSet,
+    DiscountCodeViewSet,
+    RefundViewSet,
+)
 
 router = DefaultRouter()
-router.register(r'categories', CategoryViewSet)
-router.register(r'products', ProductViewSet)
-router.register(r'discounts', DiscountCodeViewSet)
 router.register(r'orders', OrderViewSet)
+router.register(r'products', ProductViewSet, basename='product')
+router.register(r'categories', CategoryViewSet, basename='category')
+router.register(r'product-images', ProductImageViewSet, basename='product-image')
+router.register(r'discount-codes', DiscountCodeViewSet, basename='discount-code')
+router.register(r'refunds', RefundViewSet, basename='refund')
 
 urlpatterns = [
     path('', include(router.urls)),
 ]
 
-# NOTE: Carrier endpoints intentionally omitted (TODO)
+# NOTE: Other endpoints (categories/products/discounts) can be added later