Move desktop and e2e into examples/ directory

- desktop/ → examples/django-react-desktop-app/
- e2e/ → examples/django-react-site/
- example/ → examples/django-react-site/backend/
- Update Dockerfile.test, Makefile, playwright config, and
  django.config.mjs path references

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

examples/django-react-site/backend/testapp/apps.py

@@ -0,0 +1,9 @@
+from django.apps import AppConfig
+
+
+class TestAppConfig(AppConfig):
+    name = "testapp"
+    default_auto_field = "django.db.models.BigAutoField"
+
+    def ready(self):
+        import testapp.mizan_clients  # noqa: F401