Fix Docker implementation for MCP protocol

[pab1it0]

Purpose

This PR fixes the issue reported in #2 where the Prometheus MCP server fails to work with Claude correctly. The root cause is related to how the server is being executed in Docker and how the stdin/stdout handling is managed for the MCP protocol.

Changes Made

The following changes have been implemented:

1. Completely Rewrote the Dockerfile:

   • Changed to a multi-stage build pattern
   • Removed the docker-entrypoint.sh script in favor of direct command execution
   • Added proper user permissions with non-root user
   • Set environment variables to ensure proper stdout handling (PYTHONUNBUFFERED=1)
   • Added healthcheck for better container monitoring

2. Added Documentation:

   • Updated README.md with information about the Docker implementation changes

Related Issues

This PR addresses the issue reported in #2 where users experience errors when using the MCP server with Claude.