fix: Resolve tickets controller Event lookup issues

- Fix Event attribute name from starts_at to start_time in orders/new view
- Update TicketsController#set_event to use session[:event_id] as fallback when params[:id] is not available
- Remove duplicate Event.find call in tickets#create action
- Fix form submission path in tickets/new to use parameterless route
- Add debug logging to troubleshoot event ID resolution
- Update redirect paths to use proper route helpers

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

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

app/views/orders/new.html.erb

@@ -14,9 +14,9 @@
         <div class="mb-6">
           <h3 class="text-lg font-medium text-gray-800"><%= @event.name %></h3>
           <p class="text-gray-600"><%= @event.venue_name %></p>
-          <% if @event.starts_at %>
+          <% if @event.start_time %>
             <p class="text-sm text-gray-500">
-              <%= @event.starts_at.strftime("%d/%m/%Y à %H:%M") %>
+              <%= @event.start_time.strftime("%d/%m/%Y à %H:%M") %>
             </p>
           <% end %>
         </div>

app/views/tickets/new.html.erb

@@ -98,7 +98,7 @@
             les billets.</p>
         </div>
 
-        <%= form_with url: ticket_create_path(@event.slug, @event), method: :post, local: true, class: "space-y-8" do |form| %>
+        <%= form_with url: ticket_create_path, method: :post, local: true, class: "space-y-8" do |form| %>
           <% if @tickets_needing_names.any? %>
             <div class="space-y-6">
               <div class="flex items-center justify-center mb-2">