feat: Add Fly.io deployment configuration and GitHub Actions workflow

[StuartF303]

This adds complete Fly.io cloud deployment support with automatic GitHub Actions deployment.

New Files:

• fly.api.toml: Fly.io configuration for API backend
• fly.web.toml: Fly.io configuration for Web frontend
• docker/Dockerfile.api.prod: Production API Dockerfile (port 8080)
• docker/Dockerfile.web.prod: Production Web Dockerfile with nginx
• docker/nginx.prod.conf: Nginx config template with API URL substitution
• .github/workflows/deploy-fly.yml: GitHub Actions deployment workflow
• DEPLOYMENT.md: Quick deployment reference guide
• docs/deployment/fly-io-deployment.md: Comprehensive Fly.io deployment guide

Features:

• Two-app architecture (API + Web) for optimal resource usage
• Auto-scaling: Scale to zero when idle, auto-start on request
• GitHub Actions auto-deployment on push to main
• Environment variable support for API URL configuration
• Health checks for both API and Web
• Minimal resource usage (512MB API, 256MB Web) to fit free tier

Configuration:

• Primary region: iad (Ashburn, Virginia)
• API: 1 shared CPU, 512MB RAM, port 8080
• Web: 1 shared CPU, 256MB RAM, port 8080
• HTTPS enforced on both applications

Deployment:

• Manual: flyctl deploy --config fly.api.toml
• Auto: Push to main branch (requires FLY_API_TOKEN secret)

Documentation:

• Updated README.md with cloud deployment section
• Full deployment guide with troubleshooting
• GitHub Actions setup instructions
• Cost optimization tips