fix: Update views and controllers for event image display

Update all event-related view templates and controllers to properly handle and display event images throughout the application.

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

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

app/views/promoter/events/new.html.erb

@@ -63,7 +63,7 @@
           <%= form.label :image, "Image de couverture", class: "block text-sm font-medium text-gray-700 mb-2" %>
           <div class="space-y-4">
             <!-- Current image preview (for edit mode) -->
-            <% if @event.image.attached? %>
+            <% if @event.has_image? %>
               <div class="relative">
                 <%= image_tag @event.image.variant(resize_to_limit: [400, 225]), class: "w-full h-48 object-cover rounded-lg border border-gray-200" %>
                 <div class="absolute top-2 right-2">