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/views/ticket_mailer/event_reminder.html.erb

@@ -45,6 +45,7 @@
             <div>
               <p style="margin: 0 0 5px; font-weight: bold; color: #212529;">🎫 Billet #<%= index + 1 %></p>
               <p style="margin: 0; color: #6c757d; font-size: 14px;"><%= ticket.ticket_type.name %></p>
+              <p style="margin: 5px 0 0;"><a href="<%= ticket_url(ticket) %>" style="color: #4c1d95; text-decoration: none; font-size: 14px;">📱 Voir le détail et le code QR</a></p>
             </div>
             <div style="text-align: right;">
               <span style="background-color: #d4edda; color: #155724; padding: 4px 8px; border-radius: 4px; font-size: 12px; font-weight: bold;">ACTIF</span>