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/views/events/show.html.erb

@@ -208,8 +208,12 @@
 
             <!-- Right Column: Ticket Selection -->
             <div class="lg:col-span-1">
-              <%= form_with url: event_checkout_path(@event.slug, @event), method: :post, id: "checkout_form", local: true, data: { controller: "ticket-selection" } do |form| %>
-
+              <%= form_with url: "#", method: :post, id: "checkout_form", local: true, data: { 
+              controller: "ticket-selection", 
+              ticket_selection_target: "form",
+              ticket_selection_event_slug_value: @event.slug,
+              ticket_selection_event_id_value: @event.id
+            } do |form| %>
 
               <div class="">
                 <div