Card piani: un solo stile di bordo grigio per tutte e tre.

Rimuove featured con contorno rosso che creava 2 card rosse e 1 grigia.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/views/shared/_plan_cards.html.erb

@@ -14,8 +14,7 @@
          stripe_subscription_active: stripe_subscription_active?(subscription),
          current_interval: current_interval
        ) : nil %>
-    <% featured = billing_mode ? (plan.slug == current_slug) : (plan.slug == "premium_light") %>
-    <div class="plan-card<%= " featured" if featured %>">
+    <div class="plan-card">
       <h3><%= plan.name %></h3>
       <% if plan.slug == "free" %>
         <div class="plan-price">€0</div>