feat: Implement complete ticket purchasing flow with new TicketsController

- Create new TicketsController with actions for name collection, creation, and checkout
- Add dedicated ticket views (new.html.erb, checkout.html.erb, show.html.erb)
- Update ticket_selection_controller.js to handle form submission via AJAX
- Add store_cart endpoint in EventsController for session-based cart management
- Update routes to support new ticket flow: /tickets/new, /create, /checkout
- Fix attribute name consistency across views (title→name, starts_at→start_time)
- Add Stripe checkout integration with proper error handling
- Remove deprecated collect_names flow in favor of streamlined approach

The flow is now: Event selection → AJAX cart storage → Name collection → Checkout → Payment

app/helpers/tickets_helper.rb

@@ -0,0 +1,2 @@
+module TicketsHelper
+end