fix: TopNav 모바일 오버레이 body scroll lock + 푸터 연도 2026 통일

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

app/components/TopNav.tsx

@@ -26,6 +26,14 @@ export default function TopNav() {
 
   useEffect(() => { setOpen(false); }, [pathname]);
 
+  useEffect(() => {
+    if (open) {
+      const prev = document.body.style.overflow;
+      document.body.style.overflow = 'hidden';
+      return () => { document.body.style.overflow = prev; };
+    }
+  }, [open]);
+
   const isActive = (href: string) =>
     href === '/' ? pathname === '/' : pathname.startsWith(href);