fix(web): add .pillar-card to scroll-reveal observer selector

The three-pillar cards had class 'reveal' in HTML which sets opacity:0,
but the IntersectionObserver in main.js did not include .pillar-card in
its querySelectorAll list. The cards were never observed and never got
the .visible class, making them permanently invisible.

web/js/main.js

@@ -80,7 +80,7 @@ document.addEventListener('DOMContentLoaded', () => {
   // --------------------------------------------------------
   const revealElements = document.querySelectorAll(
     '.about-card, .dimension-card, .feature-card, .role-card, ' +
-    '.stat, .contact-item, .cta-card, .product-quote'
+    '.stat, .contact-item, .cta-card, .product-quote, .pillar-card'
   );
 
   if (revealElements.length) {