Allow self-signed and unverified SSL certificates in Mailconv SMTP transport

[mysubcult]

Summary of Changes

This PR sets SMTPOptions with relaxed SSL verification in erLhcoreClassMailconvValidator::setSendParameters().

Context & Problem

• When sending emails or replies in Mailconv (sendEmail, sendReply, or the "Test SMTP" button in the mailbox edit modal), PHPMailer defaults to strict SSL certificate verification (verify_peer = true, verify_peer_name = true).
• If an administrator uses a self-hosted mail server (e.g., Stalwart, Mailcow, Postfix, or internal mail relays) with self-signed SSL certificates, private CA certificates, or hostname variations, PHPMailer fails during the TLS handshake:

  stream_socket_client(): SSL operation failed with code 1. OpenSSL Error messages:
  error:0A000086:SSL routines::certificate verify failed
  stream_socket_client(): Failed to enable crypto
  SMTP connect() failed.
  

• While IMAP incoming mail configuration allows flags such as /novalidate-cert (e.g. {mail.example.com:993/imap/ssl/novalidate-cert}), there was no setting or option in Mailconv to configure SMTPOptions for outbound SMTP sending.
• Live Helper Chat already has this exact configuration in core for standard chat mail in lhc_web/lib/core/lhchat/lhchatmail.php (lines 37–51: // To work with various SMTP servers).

Fix

• Added SMTPOptions to erLhcoreClassMailconvValidator::setSendParameters() to allow self-signed and unverified SSL certificates, bringing consistency between standard chat mail delivery and Mailconv outbound delivery.