Add walkthrough card styling

index.html

@@ -87,6 +87,9 @@
         .category-card.baby { border-color: #f59e0b; }
         .category-card.baby:hover { box-shadow: 0 25px 50px rgba(245, 158, 11, 0.3); }
 
+        .category-card.walkthrough { border-color: #10b981; }
+        .category-card.walkthrough:hover { box-shadow: 0 25px 50px rgba(16, 185, 129, 0.3); }
+
         .category-card.developer { border-color: #ef4444; }
         .category-card.developer:hover { box-shadow: 0 25px 50px rgba(239, 68, 68, 0.3); }