feat: Implement comprehensive event management system for promoters

This commit adds a complete event management interface allowing promoters to 
create, edit, and manage their events with full CRUD operations.

## Backend Features
- New Promoter::EventsController with full CRUD operations
- Event state management (draft, published, canceled, sold_out)
- User authorization system with can_manage_events? method
- Proper scoping to ensure users only see their own events

## Frontend Features  
- Modern responsive UI with Tailwind CSS styling
- Event listing with status indicators and quick actions
- Comprehensive event creation and editing forms
- Detailed event show page with metrics and management options
- Integration with main dashboard via promoter action buttons

## JavaScript Improvements
- Refactored inline JavaScript to dedicated Stimulus controller
- Auto-slug generation from event names with proper sanitization
- Improved code organization following Rails conventions

## Routes & Navigation
- Namespaced promoter routes under /promoter/
- RESTful endpoints with state management actions
- Proper breadcrumb navigation and user flow

## Files Added/Modified
- app/controllers/promoter/events_controller.rb (new)
- app/javascript/controllers/event_form_controller.js (new) 
- app/views/promoter/events/*.html.erb (4 new view files)
- app/models/user.rb (added authorization methods)
- app/views/pages/dashboard.html.erb (added promoter buttons)
- config/routes.rb (added promoter namespace)
- app/javascript/controllers/index.js (registered new controller)

🎯 Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

config/routes.rb

@@ -34,6 +34,18 @@ Rails.application.routes.draw do
   # === Pages ===
   get "dashboard", to: "pages#dashboard", as: "dashboard"
 
+  # === Promoter Routes ===
+  namespace :promoter do
+    resources :events do
+      member do
+        patch :publish
+        patch :unpublish
+        patch :cancel
+        patch :mark_sold_out
+      end
+    end
+  end
+
   # === Events ===
   get "events",                      to: "events#index",           as: "events"
   get "events/:slug.:id",            to: "events#show",            as: "event"