Frontend build (Vite)

- Development: run `npm run frontend:dev` in the project root, which starts Vite. Open the dev server URL printed by Vite (usually http://localhost:5173) and the backend at `http://localhost:8282`.
- Build: run `npm run frontend:build` which outputs files to `dist/`. The Express server will serve `dist/index.html` at `/admin` once `dist/` exists.

Notes:
- Install dev dependencies with `npm install` before running the scripts.
- The Vite build includes `@vitejs/plugin-legacy` for broader browser support.