docs: add comprehensive Vercel setup guide

- Step-by-step deployment instructions
- Environment variable configuration
- OpenTelemetry setup options (Honeycomb, Jaeger, none)
- GitHub Actions integration guide
- Monitoring and debugging procedures
- Cost optimization tips
- Troubleshooting common issues

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: PaulJPhilp