Update AreaTabs and experimenta page for educator annual pass visibility

- Disabled the educator tab in AreaTabs and added a 'Demnächst' badge for future visibility.
- Updated the experimenta page header to singular form for consistency and improved layout of ProductCard components for better readability.

These changes enhance the user experience by clarifying product availability and improving the overall presentation of the educator annual pass.

app/components/navigation/AreaTabs.vue

@@ -26,8 +26,9 @@ const areas: ProductArea[] = [
     id: 'educator',
     label: 'Pädagogen Jahreskarte',
     icon: GraduationCap,
-    enabled: true,
+    enabled: false,
     visible: true,
+    badge: 'Demnächst',
     route: '/educator',
   },
   {