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>

playwright.config.ts

@@ -1,7 +1,7 @@
 import { defineConfig } from '@playwright/test'
 
 export default defineConfig({
-    testDir: './e2e',
+    testDir: './examples/django-react-site',
     timeout: 15000,
     retries: 0,
     reporter: 'list',