Add shopping cart and product review features

Introduces Cart and CartItem models, admin, serializers, and API endpoints for shopping cart management for both authenticated and anonymous users. Adds Review model, serializers, and endpoints for product reviews, including public creation and retrieval. Updates ProductImage ordering, enhances order save logic with notification, and improves product and order endpoints with new actions and filters. Includes related migrations for commerce, configuration, social chat, and Deutsche Post integration.

backend/configuration/migrations/0002_siteconfiguration_deutschepost_api_url_and_more.py

@@ -0,0 +1,38 @@
+# Generated by Django 5.2.7 on 2026-01-17 01:37
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('configuration', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='siteconfiguration',
+            name='deutschepost_api_url',
+            field=models.URLField(default='https://gw.sandbox.deutschepost.com', help_text='Deutsche Post API URL (sandbox/production)', max_length=255),
+        ),
+        migrations.AddField(
+            model_name='siteconfiguration',
+            name='deutschepost_client_id',
+            field=models.CharField(blank=True, help_text='Deutsche Post OAuth Client ID', max_length=255, null=True),
+        ),
+        migrations.AddField(
+            model_name='siteconfiguration',
+            name='deutschepost_client_secret',
+            field=models.CharField(blank=True, help_text='Deutsche Post OAuth Client Secret', max_length=255, null=True),
+        ),
+        migrations.AddField(
+            model_name='siteconfiguration',
+            name='deutschepost_customer_ekp',
+            field=models.CharField(blank=True, help_text='Deutsche Post Customer EKP number', max_length=20, null=True),
+        ),
+        migrations.AddField(
+            model_name='siteconfiguration',
+            name='deutschepost_shipping_price',
+            field=models.DecimalField(decimal_places=2, default=150, help_text='Default Deutsche Post shipping price', max_digits=10),
+        ),
+    ]