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>

BACKLOG.md

@@ -9,14 +9,11 @@
 ### Medium Priority
 
 - [ ] feat: Promoter system with event creation, ticket types creation and metrics display
-- [ ] feat: Multiple ticket types (early bird, VIP, general admission)
 - [ ] feat: Refund management system
 - [ ] feat: Real-time sales analytics dashboard
 - [ ] feat: Guest checkout without account creation
 - [ ] feat: Seat selection with interactive venue maps
 - [ ] feat: Dynamic pricing based on demand
-- [ ] feat: Profesionnal account. User can ask to change from a customer to a professionnal account to create and manage events.
-- [ ] feat: User can choose to create a professionnal account on sign-up page to be allowed to create and manage events
 - [ ] feat: Payout system for promoters (automated/manual payment processing)
 - [ ] feat: Platform commission tracking and fee structure display
 - [ ] feat: Tax reporting and revenue export for promoters
@@ -53,7 +50,6 @@
 
 ## 🚧 Doing
 
-- [ ] feat: Promotion code on ticket
 - [ ] feat: Page to display all tickets for an event
 - [ ] feat: Add a link into notification email to order page that display all tickets
 
@@ -65,7 +61,11 @@
 - [x] Add login functionality
 - [x] refactor: Moving checkout to OrdersController
 - [x] feat: Payment gateway integration (Stripe) - PayPal not implemented
+- [x] feat: Profesionnal account. User can ask to change from a customer to a professionnal account to create and manage events.
 - [x] feat: Digital tickets with QR codes
 - [x] feat: Ticket inventory management and capacity limits
 - [x] feat: Event discovery with search and filtering
+- [x] feat: Multiple ticket types (early bird, VIP, general admission)
 - [x] feat: Email notifications (purchase confirmations, event reminders)
+- [x] feat: Promotion code on ticket
+- [x] feat: User can choose to create a professionnal account on sign-up page to be allowed to create and manage events