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- Deleted several outdated scripts: `create_test_users.py`, `test_image_write_access.py`, `update_free_plan.py`, and the database file `db.sqlite3` to clean up the backend.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

frontend/src/components/shared/templates/LandingTemplate.tsx

@@ -0,0 +1,26 @@
+import type { ReactNode } from 'react';
+import { MinimalLayout } from '../layouts/MinimalLayout';
+
+export interface LandingTemplateProps {
+  hero: ReactNode;
+  highlights: ReactNode[];
+  background?: 'light' | 'dark';
+}
+
+export function LandingTemplate({ hero, highlights, background }: LandingTemplateProps) {
+  return (
+    <MinimalLayout background={background}>
+      <div className="shared-landing">
+        <div className="shared-landing__hero">{hero}</div>
+        <div className="shared-landing__highlights">
+          {highlights.map((highlight, index) => (
+            // eslint-disable-next-line react/no-array-index-key
+            <div key={index}>{highlight}</div>
+          ))}
+        </div>
+      </div>
+    </MinimalLayout>
+  );
+}
+
+