fix: vertically center about page hero content using page-hero class

Replaced custom py-16/py-20 padding with the standard page-hero class
so the hero content is properly centered like on other pages.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/about/page.tsx

@@ -11,7 +11,7 @@ export default function AboutPage() {
   return (
     <>
       {/* Hero */}
-      <section className="py-16 md:py-20 flex flex-col items-center justify-center text-center px-6">
+      <section className="page-hero flex flex-col items-center justify-center text-center px-6">
         <div className="max-w-4xl mx-auto">
           <p className="font-sans-alt text-xs tracking-[0.2em] text-[var(--accent-gold)] mb-4">
             THE ARTIST