feat: Add configurable HOST binding for production deployments

[guram-evinced]

Summary

This PR adds support for configurable HOST binding address to enable deployment in containerized environments like Docker and Kubernetes.

Changes

Core Implementation

• src/config.ts: Added HOST environment variable with default 127.0.0.1
• src/sse_server.ts: Updated HTTP and HTTPS server binding to use configurable HOST

Documentation

• README.md: Added HOST to configuration options table
• docs/sse-transport.md: Added HOST configuration and usage examples

Motivation

The server was hardcoded to bind to 127.0.0.1 (localhost only), which prevented external access in production environments:

• Kubernetes deployments couldn't receive health probe requests
• Docker containers couldn't expose the server externally
• Load balancers and ingress controllers couldn't reach the server

Solution

Added a configurable HOST environment variable that:

• Defaults to 127.0.0.1: Maintains secure localhost binding for local development
• Allows 0.0.0.0: Enables external access when explicitly configured via environment variable
• No breaking changes: Existing installations continue to work without modification

Usage

Local Development (Default)

# Binds to 127.0.0.1 (localhost only)
npx @taazkareem/clickup-mcp-server

Production/Kubernetes

# Binds to 0.0.0.0 (external access)
HOST=0.0.0.0 PORT=8080 ENABLE_SSE=true npx @taazkareem/clickup-mcp-server

Kubernetes Deployment

env:
  - name: HOST
    value: "0.0.0.0"
  - name: PORT
    value: "8080"
  - name: ENABLE_SSE
    value: "true"

Security Considerations

✅ Secure by default: Defaults to 127.0.0.1 (localhost only)
✅ Opt-in for production: Requires explicit HOST=0.0.0.0 configuration
✅ No breaking changes: Existing users unaffected
✅ Works with existing security features: Compatible with HTTPS, origin validation, rate limiting

Testing

Tested in production Kubernetes cluster:

• ✅ Health probes working correctly
• ✅ Ingress routing functional
• ✅ Service discovery operational
• ✅ Local development unaffected

Related Issues

This enables proper deployment in containerized environments and resolves binding issues in Kubernetes.

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CC: @taazkareem - This change enables the ClickUp MCP Server to run in production Kubernetes environments while maintaining secure defaults for local development.