Use error instead of log to prevent stdio errors

[mqln]

If you run the existing code, and connect with Claude Desktop, then the client will function but still report an error of,

Unexpected token 'A', "Apollo.io "... is not valid JSON {"context":"connection","stack":"SyntaxError: Unexpected token 'A', \"Apollo.io \"... is not valid JSON\n    at JSON.parse (<anonymous>)\n...

This is due to the line after the server init,

console.log('Apollo.io MCP server started');

Since we're in a stdio session, the log is being fed directly to the client, which cannot be read. The common workaround for this is to just use console.error, which is referenced in the Google Drive example.