Feature Request: Add Twilio SMS Notification Support

Is your feature request related to a problem? Please describe.
Currently, users need alternative notification methods for critical alerts. SMS notifications via Twilio would provide reliable, real-time alerts that don't depend on email or other channels.

Describe the solution you'd like
Add Twilio SMS as a notification channel option. Users should be able to:

• Configure Twilio credentials (Account SID, Auth Token, Phone Number) in settings
• Select Twilio SMS as a notification method when setting up monitors
• Receive SMS alerts when monitors go down or recover

Describe alternatives you've considered

• Email notifications (already available but may not be checked immediately)
• Other SMS providers (Twilio is widely used and reliable)

Additional context
Screenshots and implementation details will be provided in the pull request.