fix: resolve TypeScript build error in notifyMail SMTP transporter

[Atanu2k4]

Summary

Fixes a TypeScript compilation error introduced when adding Railway-specific SMTP options
(family, connectionTimeout, etc.) to the Nodemailer transporter. The family: 4
property is not present in Nodemailer's default TransportOptions type, causing the build
to fail with a "No overload matches this call" error.

Related issue

Fixes #62

Changes

• Added import type SMTPTransport from "nodemailer/lib/smtp-transport" in lib/notifyMail.ts
• Cast the createTransport(...) options object as SMTPTransport.Options to satisfy TypeScript
  while preserving all runtime SMTP settings (family: 4, timeouts, TLS config)

Testing

• npm run build completes successfully with no TypeScript errors
• All 31 routes compile and generate correctly

Checklist

• Title follows the repository PR format
• The issue is linked with Fixes #62
• Testing notes are included

[github-actions]

✅ PR Validation Passed

Your PR title and description meet all requirements:

• Title follows conventional format
• All required sections are present
• Issue is properly linked (BUG: smtp not working #62)