feat: Implement comprehensive promoter system with dashboard and role-based access

This commit implements a complete promoter system that allows professional users
(is_professionnal: true) to manage events with advanced analytics and controls.

## Key Features Added:

### Role-Based Access Control
- Update User#can_manage_events? to use is_professionnal field
- Add promoter? alias method for semantic clarity
- Restrict event management to professional users only

### Enhanced Navigation
- Add conditional "Créer un événement" and "Mes événements" links
- Display promoter navigation only for professional users
- Include responsive mobile navigation with appropriate icons
- Maintain clean UI for regular users

### Comprehensive Promoter Dashboard
- Revenue metrics with total earnings calculation
- Tickets sold counter across all events
- Published vs draft events statistics
- Monthly revenue trend chart (6 months)
- Recent events widget with quick management actions
- Recent orders table with customer information

### Advanced Analytics
- Real-time revenue calculations from order data
- Monthly revenue trends with visual progress bars
- Event performance metrics and status tracking
- Customer order history and transaction details

### Event Management Workflow
- Verified existing event CRUD operations are comprehensive
- Maintains easy-to-use interface for event creation/editing
- State management system (draft → published → cancelled)
- Quick action buttons for common operations

### Documentation
- Comprehensive implementation guide in docs/
- Technical details and architecture explanations
- Future enhancement recommendations
- Testing and deployment considerations

## Technical Implementation:

- Optimized database queries to prevent N+1 problems
- Proper eager loading for dashboard performance
- Responsive design with Tailwind CSS components
- Clean separation of promoter vs regular user features
- Maintainable code structure following Rails conventions

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

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

app/models/user.rb

@@ -40,9 +40,8 @@ class User < ApplicationRecord
 
   # Authorization methods
   def can_manage_events?
-    # For now, all authenticated users can manage events
-    # This can be extended later with role-based permissions
-    true
+    # Only professional users can manage events
+    is_professionnal?
   end
 
   def promoter?