Fix WCAG contrast on events page and add width/height to logo

- Labels and card text: text-gray-400 -> text-gray-600 on #fbfbfb bg
- Empty state message: text-gray-400 -> text-gray-600 on white bg
- Add explicit width/height to navbar logo to prevent CLS

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

templates/base.html.twig

@@ -90,7 +90,7 @@
             <div class="flex justify-between items-center h-20">
                 <div class="flex-shrink-0">
                     <a href="{{ path('app_home') }}" class="flex items-center group" aria-label="E-Ticket - Retour a l'accueil">
-                        <img class="h-8 md:h-12 w-auto" src="{{ 'logo.png' | imagine_filter('navbar_logo') }}" alt="E-Ticket" loading="eager">
+                        <img class="h-8 md:h-12 w-auto" src="{{ 'logo.png' | imagine_filter('navbar_logo') }}" alt="E-Ticket" loading="eager" width="48" height="48">
                     </a>
                 </div>