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>

app/jobs/event_reminder_scheduler_job.rb

@@ -41,4 +41,4 @@ class EventReminderSchedulerJob < ApplicationJob
       EventReminderJob.perform_later(event.id, 0)
     end
   end
-end
+end