feat: add mobile layout detection

src/web/components/useIsMobile.ts

@@ -0,0 +1,16 @@
+import { useEffect, useState } from 'react';
+
+export function useIsMobile(breakpoint = 768) {
+  const [isMobile, setIsMobile] = useState(() => (
+    typeof window !== 'undefined' ? window.innerWidth < breakpoint : false
+  ));
+
+  useEffect(() => {
+    const update = () => setIsMobile(window.innerWidth < breakpoint);
+    update();
+    window.addEventListener('resize', update);
+    return () => window.removeEventListener('resize', update);
+  }, [breakpoint]);
+
+  return isMobile;
+}