feat: Implement comprehensive email notifications system

This commit implements a complete email notifications system for purchase
confirmations and event reminders as requested in the medium priority
backlog tasks.

## Features Added

### Purchase Confirmation Emails
- Automatically sent when orders are marked as paid
- Supports both single tickets and multi-ticket orders
- Includes PDF ticket attachments
- Professional HTML and text templates in French

### Event Reminder Emails
- Automated reminders sent 7 days, 1 day, and day of events
- Only sent to users with active tickets
- Smart messaging based on time until event
- Venue details and ticket information included

### Background Jobs
- EventReminderJob: Sends reminders to all users for a specific event
- EventReminderSchedulerJob: Daily scheduler to queue reminder jobs
- Proper error handling and logging

### Email Templates
- Responsive HTML templates with ApéroNight branding
- Text fallbacks for better email client compatibility
- Dynamic content based on number of tickets and time until event

### Configuration & Testing
- Environment-based SMTP configuration for production
- Development setup with MailCatcher support
- Comprehensive test suite with mocking for PDF generation
- Integration tests for end-to-end functionality
- Documentation with usage examples

## Technical Implementation
- Enhanced TicketMailer with new notification methods
- Background job scheduling via Rails initializer
- Order model integration for automatic purchase confirmations
- Proper associations handling for user/ticket relationships
- Configurable via environment variables

## Files Added/Modified
- Enhanced app/mailers/ticket_mailer.rb with order support
- Added app/jobs/event_reminder_*.rb for background processing
- Updated email templates in app/views/ticket_mailer/
- Added automatic scheduling in config/initializers/
- Comprehensive test coverage in test/ directory
- Complete documentation in docs/email-notifications.md

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

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

config/initializers/event_reminder_scheduler.rb

@@ -0,0 +1,21 @@
+# Schedule event reminder notifications
+Rails.application.config.after_initialize do
+  # Only schedule in production or when SCHEDULE_REMINDERS is set
+  if Rails.env.production? || ENV["SCHEDULE_REMINDERS"] == "true"
+    # Schedule the reminder scheduler to run daily at 9 AM
+    begin
+      # Use a simple cron-like approach with ActiveJob
+      # This will be handled by solid_queue in production
+      EventReminderSchedulerJob.set(wait_until: next_run_time).perform_later
+    rescue StandardError => e
+      Rails.logger.warn "Could not schedule event reminders: #{e.message}"
+    end
+  end
+end
+
+def next_run_time
+  # Schedule for 9 AM today, or 9 AM tomorrow if it's already past 9 AM
+  target_time = Time.current.beginning_of_day + 9.hours
+  target_time += 1.day if Time.current > target_time
+  target_time
+end