fix: Docker stdio communication for Claude Desktop compatibility

Fixed the initialization timeout issue with minimal changes:

1. Added stdout flush after server connection to combat Docker buffering
2. Fixed docker-entrypoint.sh to not output to stdout in stdio mode
3. Added process.stdin.resume() to keep server alive
4. Added IS_DOCKER environment variable for future use
5. Updated README to prioritize Docker with correct -i flag configuration

The core issue was Docker's block buffering preventing immediate JSON-RPC
responses. The -i flag maintains stdin connection, and explicit flushing
ensures responses reach Claude Desktop immediately.

Also fixed "Shutting down..." message that was breaking JSON-RPC protocol
by redirecting it to stderr in stdio mode.

Docker is now the recommended installation method as originally intended.

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

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

Dockerfile

@@ -76,6 +76,9 @@ RUN chmod +x /usr/local/bin/docker-entrypoint.sh
 # Switch to non-root user
 USER nodejs
 
+# Set Docker environment flag
+ENV IS_DOCKER=true
+
 # Expose HTTP port
 EXPOSE 3000