Implement order notification system

Add notifications for order status changes.

Notification Channels:

• Email (primary)
• SMS (for critical updates)
• Push notifications (mobile app)
• In-app notifications

Notification Triggers:

• Order confirmed
• Order shipped (with tracking link)
• Order delivered
• Order cancelled
• Delivery delayed

Implementation:

• Create notification service/adapter
• Design email templates
• Integrate email provider (SendGrid/SES)
• Add SMS provider (Twilio)
• Implement notification preferences
• Add notification queue for reliability
• Track notification delivery status