Add site builder service to Docker Compose and remove obsolete scripts

- Introduced a new service `igny8_site_builder` in `docker-compose.app.yml` for site building functionality, including environment variables and volume mappings.
- Deleted several outdated scripts: `create_test_users.py`, `test_image_write_access.py`, `update_free_plan.py`, and the database file `db.sqlite3` to clean up the backend.
- Updated Django settings and URL configurations to integrate the new site builder module.

site-builder/src/main.tsx

@@ -0,0 +1,13 @@
+import { StrictMode } from 'react';
+import { createRoot } from 'react-dom/client';
+import { BrowserRouter } from 'react-router-dom';
+import './index.css';
+import App from './App.tsx';
+
+createRoot(document.getElementById('root')!).render(
+  <StrictMode>
+    <BrowserRouter>
+      <App />
+    </BrowserRouter>
+  </StrictMode>,
+);