Update homepage hero

Replace the minimal homepage with a two-column hero for ZXDB and NextReg.

Signed-off-by: codex@lucy.xalior.com

src/app/page.tsx

@@ -1,15 +1,45 @@
-import styles from "./page.module.css";
-import Link from 'next/link';
+import Link from "next/link";
 
 export default function Home() {
   return (
-    <div className={styles.page}>
-      <main className={styles.main}>
+    <div className="container-fluid py-4">
+      <div className="row g-3">
+        <div className="col-lg-6">
+          <div className="card h-100 shadow-sm">
+            <div className="card-body d-flex flex-column gap-3">
+              <div className="d-flex align-items-center gap-3">
+                <span className="bi bi-collection" style={{ fontSize: 40 }} aria-hidden />
+                <div>
+                  <h1 className="h3 mb-1">ZXDB Explorer</h1>
+                  <p className="text-secondary mb-0">Search entries, releases, magazines, and labels.</p>
+                </div>
+              </div>
+              <div className="d-flex flex-wrap gap-2">
+                <Link className="btn btn-primary" href="/zxdb">Open ZXDB</Link>
+              </div>
+              <div className="text-secondary small">Built for deep linking and fast filters.</div>
+            </div>
+          </div>
+        </div>
 
-        <Link href="/registers">
-          Register Explorer →
-        </Link>
-      </main>
+        <div className="col-lg-6">
+          <div className="card h-100 shadow-sm">
+            <div className="card-body d-flex flex-column gap-3">
+              <div className="d-flex align-items-center gap-3">
+                <span className="bi bi-cpu" style={{ fontSize: 40 }} aria-hidden />
+                <div>
+                  <h2 className="h3 mb-1">NextReg Explorer</h2>
+                  <p className="text-secondary mb-0">Browse Spectrum Next registers and bitfields.</p>
+                </div>
+              </div>
+              <div className="d-flex flex-wrap gap-2">
+                <Link className="btn btn-primary" href="/registers">Open registers</Link>
+              </div>
+              <div className="text-secondary small">Parsed locally from official NextReg definitions.</div>
+            </div>
+          </div>
+        </div>
+      </div>
     </div>
   );
 }