feat: Complete email notifications system with comprehensive functionality

- Implement comprehensive email notification system for ticket purchases and event reminders
- Add event reminder job with configurable scheduling
- Enhance ticket mailer with QR code generation and proper formatting
- Update order model with email delivery tracking
- Add comprehensive test coverage for all email functionality
- Configure proper mailer settings and disable annotations
- Update backlog to reflect completed email features

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

config/initializers/event_reminder_scheduler.rb

@@ -18,4 +18,4 @@ def next_run_time
   target_time = Time.current.beginning_of_day + 9.hours
   target_time += 1.day if Time.current > target_time
   target_time
-end
+end