feat: Implement event image upload system for promoters

- Add Active Storage migrations for file attachments
- Update Event model to handle image uploads with validation
- Replace image URL fields with file upload in forms
- Add client-side image preview with validation
- Update all views to display uploaded images properly
- Fix JSON serialization to prevent stack overflow in API
- Add custom image validation methods for format and size
- Include image processing variants for different display sizes
- Fix promotion code test infrastructure and Stripe configuration

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

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

debug_promotion_test.rb

@@ -0,0 +1,74 @@
+#!/usr/bin/env ruby
+
+# Debug script to understand the test failure
+require_relative './config/environment'
+
+# Load test data
+user = User.find_by(email: 'user1@example.com')
+event = Event.find_by(name: 'Summer Concert')
+
+puts "User: #{user.inspect}"
+puts "Event: #{event.inspect}"
+
+# Create a new order for the test
+order = user.orders.create!(event: event, status: "draft", expires_at: 15.minutes.from_now, total_amount_cents: 2000)
+puts "Order: #{order.inspect}"
+
+# Create ticket type and ticket
+ticket_type = TicketType.create!(
+  name: "Test Ticket Type",
+  description: "A valid description for the ticket type that is long enough",
+  price_cents: 2000,
+  quantity: 10,
+  sale_start_at: Time.current,
+  sale_end_at: Time.current + 1.day,
+  requires_id: false,
+  event: event
+)
+
+ticket = Ticket.create!(
+  order: order,
+  ticket_type: ticket_type,
+  status: "draft",
+  first_name: "John",
+  last_name: "Doe",
+  price_cents: 2000
+)
+
+puts "Ticket: #{ticket.inspect}"
+puts "Ticket valid?: #{ticket.valid?}"
+puts "Order tickets count: #{order.tickets.count}"
+
+# Recalculate the order total
+order.calculate_total!
+puts "Order total: #{order.total_amount_cents}"
+
+# Create a unique promotion code
+unique_code = "TESTDISCOUNT_#{SecureRandom.hex(4)}"
+puts "Creating promotion code with code: #{unique_code}"
+
+promotion_code = PromotionCode.create(
+  code: unique_code,
+  discount_amount_cents: 500,
+  expires_at: 1.month.from_now,
+  active: true,
+  user: user,
+  event: event
+)
+
+puts "Promotion code: #{promotion_code.inspect}"
+puts "Promotion code valid?: #{promotion_code.valid?}"
+
+# Check if order already has promotion codes
+puts "Order promotion codes before: #{order.promotion_codes.count}"
+
+# Try to apply the promotion code
+begin
+  order.promotion_codes << promotion_code
+  puts "Successfully added promotion code to order"
+rescue => e
+  puts "Error adding promotion code: #{e.message}"
+  puts e.backtrace.first(5)
+end
+
+puts "Order promotion codes after: #{order.promotion_codes.count}"