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- Deleted several outdated scripts: `create_test_users.py`, `test_image_write_access.py`, `update_free_plan.py`, and the database file `db.sqlite3` to clean up the backend.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

@@ -0,0 +1,18 @@
+# Site Builder Dev Image (Node 22 to satisfy Vite requirements)
+FROM node:22-alpine
+
+WORKDIR /app
+
+# Copy package manifests first for better caching
+COPY package*.json ./
+
+RUN npm install
+
+# Copy source (still bind-mounted at runtime, but needed for initial run)
+COPY . .
+
+EXPOSE 5175
+
+CMD ["npm", "run", "dev", "--", "--host", "0.0.0.0", "--port", "5175"]
+
+