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/models/order_email_test.rb

@@ -0,0 +1,39 @@
+require "test_helper"
+
+class OrderEmailTest < ActiveSupport::TestCase
+  def setup
+    @order = orders(:draft_order)
+  end
+
+  test "sends purchase confirmation email when order is marked as paid" do
+    # Mock the mailer to capture the call
+    TicketMailer.expects(:purchase_confirmation_order).with(@order).returns(stub(deliver_now: true))
+    
+    @order.mark_as_paid!
+    
+    assert_equal "paid", @order.status
+  end
+
+  test "activates all tickets when order is marked as paid" do
+    @order.tickets.update_all(status: "reserved")
+    
+    # Mock the mailer to avoid actual email sending
+    TicketMailer.stubs(:purchase_confirmation_order).returns(stub(deliver_now: true))
+    
+    @order.mark_as_paid!
+    
+    assert @order.tickets.all? { |ticket| ticket.status == "active" }
+  end
+
+  test "email sending is part of the transaction" do
+    # Mock mailer to raise an error
+    TicketMailer.stubs(:purchase_confirmation_order).raises(StandardError.new("Email error"))
+    
+    assert_raises(StandardError) do
+      @order.mark_as_paid!
+    end
+    
+    # Order should not be marked as paid if email fails
+    assert_equal "draft", @order.reload.status
+  end
+end