- EmailOtpService: genera/verifica codigo 6 digitos via SMTP (requiere env vars: SMTP_HOST, SMTP_USER, SMTP_PASS, EMAIL_FROM) - POST /auth/send-email-otp: envia codigo al correo indicado - POST /auth/link-email-otp: verifica codigo y vincula email+pass - nodemailer agregado como dependencia Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>