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>

app/mailers/application_mailer.rb

@@ -1,4 +1,4 @@
 class ApplicationMailer < ActionMailer::Base
-  default from: "from@example.com"
+  default from: ENV.fetch("MAILER_FROM_EMAIL", "no-reply@aperonight.fr")
   layout "mailer"
 end

app/mailers/ticket_mailer.rb

@@ -1,5 +1,25 @@
 class TicketMailer < ApplicationMailer
-  default from: "notifications@aperonight.com"
+  def purchase_confirmation_order(order)
+    @order = order
+    @user = order.user
+    @event = order.event
+    @tickets = order.tickets
+
+    # Generate PDF attachments for all tickets
+    @tickets.each do |ticket|
+      pdf = ticket.to_pdf
+      attachments["ticket-#{@event.name.parameterize}-#{ticket.qr_code[0..7]}.pdf"] = {
+        mime_type: "application/pdf",
+        content: pdf
+      }
+    end
+
+    mail(
+      to: @user.email,
+      subject: "Confirmation d'achat - #{@event.name}",
+      template_name: "purchase_confirmation"
+    )
+  end
 
   def purchase_confirmation(ticket)
     @ticket = ticket
@@ -18,4 +38,33 @@ class TicketMailer < ApplicationMailer
       subject: "Confirmation d'achat - #{@event.name}"
     )
   end
+
+  def event_reminder(user, event, days_before)
+    @user = user
+    @event = event
+    @days_before = days_before
+    
+    # Get user's tickets for this event
+    @tickets = Ticket.joins(:order, :ticket_type)
+                     .where(orders: { user: @user }, ticket_types: { event: @event }, status: "active")
+
+    return if @tickets.empty?
+
+    subject = case days_before
+              when 7
+                "Rappel : #{@event.name} dans une semaine"
+              when 1
+                "Rappel : #{@event.name} demain"
+              when 0
+                "C'est aujourd'hui : #{@event.name}"
+              else
+                "Rappel : #{@event.name} dans #{days_before} jours"
+              end
+
+    mail(
+      to: @user.email,
+      subject: subject,
+      template_name: "event_reminder"
+    )
+  end
 end