feat: add scroll-to-top button

components/ui/ScrollToTop.tsx

@@ -0,0 +1,28 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { motion } from "motion/react";
+
+export function ScrollToTop() {
+  const [visible, setVisible] = useState(false);
+
+  useEffect(() => {
+    const toggle = () => setVisible(window.scrollY > 400);
+    toggle();
+    window.addEventListener("scroll", toggle, { passive: true });
+    return () => window.removeEventListener("scroll", toggle);
+  }, []);
+
+  return (
+    <motion.button
+      type="button"
+      onClick={() => window.scrollTo({ top: 0, behavior: "smooth" })}
+      whileHover={{ scale: 1.1 }}
+      whileTap={{ scale: 0.95 }}
+      className="scroll-to-top"
+      aria-label="Scroll to top"
+    >
+      <svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round"><polyline points="18 15 12 9 6 15"/></svg>
+    </motion.button>
+  );
+}