Implement Cloudflare build process and update deployment configuration for Samplestep frontend

Commit notes

- Added `build.sh` script to automate the build process with error handling for pnpm lockfile issues. - Created `.nvmrc` for Node.js version consistency across environments. - Updated `package.json` scripts for Cloudflare deployment, including a new `build:cf` command. - Configured `wrangler.jsonc` to include build command for Cloudflare Workers. - Revised `onboarding.tsx` to enhance user experience and updated text for clarity.