Add SMTP Email Service for LDAP User Notifications

[GoliathLabs]

Changes:

• Implemented Email Service: Integrated nodemailer to send user credentials via email.
• Environment Variables: Added SMTP configuration to .env (e.g., SMTP_HOST, SMTP_USER).
• Docker Support: Loaded SMTP variables via docker-compose.yml.
• Enhanced Email Content: Includes login details and instructions to contact the Infrastructure Manager on Slack.
• Error Handling: Improved logging for authentication and connection issues.

Test Plan:

1. Set .env variables correctly and rebuild containers.
2. Trigger status change to accepted and verify email delivery.
3. Check logs for successful delivery or errors.