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>

test/jobs/event_reminder_job_test.rb

@@ -0,0 +1,31 @@
+require "test_helper"
+
+class EventReminderJobTest < ActiveJob::TestCase
+  def setup
+    @event = events(:concert_event)
+    @user = users(:one)
+    @ticket = tickets(:one)
+  end
+
+  test "performs event reminder job for users with tickets" do
+    # Mock the mailer to avoid actual email sending in tests
+    TicketMailer.expects(:event_reminder).with(@user, @event, 7).returns(stub(deliver_now: true))
+
+    EventReminderJob.perform_now(@event.id, 7)
+  end
+
+  test "handles missing event gracefully" do
+    assert_raises(ActiveRecord::RecordNotFound) do
+      EventReminderJob.perform_now(999999, 7)
+    end
+  end
+
+  test "logs error when mailer fails" do
+    # Mock a failing mailer
+    TicketMailer.stubs(:event_reminder).raises(StandardError.new("Test error"))
+    
+    Rails.logger.expects(:error).with(regexp_matches(/Failed to send event reminder/))
+    
+    EventReminderJob.perform_now(@event.id, 7)
+  end
+end