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- Deleted several outdated scripts: `create_test_users.py`, `test_image_write_access.py`, `update_free_plan.py`, and the database file `db.sqlite3` to clean up the backend.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

backend/igny8_core/urls.py

@@ -27,6 +27,7 @@ urlpatterns = [
     path('api/v1/auth/', include('igny8_core.auth.urls')),  # Auth endpoints
     path('api/v1/planner/', include('igny8_core.modules.planner.urls')),
     path('api/v1/writer/', include('igny8_core.modules.writer.urls')),
+    path('api/v1/site-builder/', include('igny8_core.modules.site_builder.urls')),
     path('api/v1/system/', include('igny8_core.modules.system.urls')),
     path('api/v1/billing/', include('igny8_core.modules.billing.urls')),  # Billing endpoints
     path('api/v1/automation/', include('igny8_core.modules.automation.urls')),  # Automation endpoints