Add Cloudflare deployment guide and configuration files

Commit notes

- Introduced a comprehensive guide for deploying the Beatstep frontend to Cloudflare Workers/Pages, detailing prerequisites, setup, deployment commands, and troubleshooting. - Updated `package.json` with new deployment scripts for Cloudflare integration. - Configured `react-router.config.ts` for server-side rendering and Cloudflare compatibility. - Created `wrangler.toml` for Cloudflare Workers deployment, including environment variable management and asset configuration.