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- Deleted several outdated scripts: `create_test_users.py`, `test_image_write_access.py`, `update_free_plan.py`, and the database file `db.sqlite3` to clean up the backend.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/App.tsx

@@ -0,0 +1,43 @@
+import { NavLink, Route, Routes } from 'react-router-dom';
+import { Wand2, LayoutTemplate, PanelsTopLeft } from 'lucide-react';
+import { WizardPage } from './pages/wizard/WizardPage';
+import { PreviewCanvas } from './pages/preview/PreviewCanvas';
+import { SiteDashboard } from './pages/dashboard/SiteDashboard';
+import './App.css';
+
+function App() {
+  return (
+    <div className="app-shell">
+      <aside className="app-sidebar">
+        <div className="brand">
+          <span>Site Builder</span>
+          <small>Phase 3 · wizard + preview</small>
+        </div>
+        <nav>
+          <NavLink to="/" end>
+            <Wand2 size={18} />
+            Wizard
+          </NavLink>
+          <NavLink to="/preview">
+            <LayoutTemplate size={18} />
+            Preview
+          </NavLink>
+          <NavLink to="/dashboard">
+            <PanelsTopLeft size={18} />
+            Blueprint history
+          </NavLink>
+        </nav>
+      </aside>
+
+      <main className="app-main">
+        <Routes>
+          <Route path="/" element={<WizardPage />} />
+          <Route path="/preview" element={<PreviewCanvas />} />
+          <Route path="/dashboard" element={<SiteDashboard />} />
+        </Routes>
+      </main>
+    </div>
+  );
+}
+
+export default App;