Update sendEmail schema and implementation to allow changing of sender name

[paul678]

Description

The MCP doesn't expose the from.name parameter, limiting sender customization. This creates a gap with the Mailtrap Transactional API, which supports:

{
  "from": {
    "email": "sender@example.com",
    "name": "Sender Name"
  }
}

Request

Expose the from.name parameter in the MCP to allow custom sender names for better branding, user recognition, and email deliverability.