feat(notifications): implement notification router with email, push, SMS support
- Add notification router (sendEmail, sendPush, sendSMS, device mgmt, prefs)
- Create provider clients: Resend, Firebase Admin (FCM), Twilio
- Add notification_preferences table to Drizzle schema
- Create branded email templates (welcome, alert, password reset, family invite, billing)
- Implement notification service with error handling and E.164 validation
- Wire router into app root
- Write unit tests with mocked providers (25 tests passing)
- Add resend, firebase-admin, twilio dependencies
Michael Freno
5154990acd