Add Docker setup for Monaco backend with Cloudflare tunnel support

new-backend/README.tunnel.md

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+# Backend with Cloudflare Tunnel
+
+This setup runs the Monaco backend service and establishes a Cloudflare tunnel, exposing the service to the internet securely via api.ishikabhoyar.tech.
+
+## Prerequisites
+
+- Docker and Docker Compose installed
+- The Cloudflare tunnel certificate (cert.pem) in the same directory as the Dockerfile.tunnel
+
+## Files
+
+- `Dockerfile.tunnel`: Dockerfile that builds the backend and sets up Cloudflare tunnel
+- `cert.pem`: Cloudflare tunnel certificate
+- `config.json`: Cloudflare tunnel configuration that routes traffic to api.ishikabhoyar.tech
+- `docker-compose.tunnel.yml`: Docker Compose configuration for easy deployment
+
+## How to Run
+
+```bash
+# Build and start the container
+docker-compose -f docker-compose.tunnel.yml up -d
+
+# Check logs
+docker-compose -f docker-compose.tunnel.yml logs -f
+```
+
+## How it Works
+
+1. The Dockerfile builds the Go backend application
+2. It installs the Cloudflare tunnel client (cloudflared)
+3. On container start:
+   - The backend server starts on port 8080
+   - The Cloudflare tunnel connects to Cloudflare's edge network using the config.json
+   - External traffic to api.ishikabhoyar.tech is routed through the tunnel to the backend
+   - The cloudflared runs entirely within the container, isolated from any host cloudflared instance
+
+## Environment Variables
+
+You can customize the behavior by modifying the environment variables in the docker-compose.tunnel.yml file:
+
+- `PORT`: The port the backend server listens on (default: 8080)
+- `CONCURRENT_EXECUTIONS`: Number of concurrent code executions (default: 5)
+- `QUEUE_CAPACITY`: Maximum queue capacity for code executions (default: 100)
+- `DEFAULT_TIMEOUT`: Default timeout for code execution in seconds (default: 30)
+- `SANDBOX_NETWORK_DISABLED`: Whether to disable network in sandbox containers (default: true)
+- `SANDBOX_PIDS_LIMIT`: Process ID limit for sandbox containers (default: 50)