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

test/fixtures/ticket_types.yml

@@ -8,6 +8,7 @@ one:
   sale_start_at: <%= 1.day.ago %>
   sale_end_at: <%= 1.day.from_now %>
   event: one
+  # minimum_age: 18
 
 two:
   name: VIP Access
@@ -16,4 +17,5 @@ two:
   quantity: 50
   sale_start_at: <%= 1.day.ago %>
   sale_end_at: <%= 1.day.from_now %>
-  event: two
+  event: two
+  # minimum_age: 18