feat: add scroll progress indicator

components/ui/ScrollProgress.tsx

@@ -0,0 +1,33 @@
+"use client";
+
+import { useEffect, useState } from "react";
+
+export function ScrollProgress() {
+  const [progress, setProgress] = useState(0);
+
+  useEffect(() => {
+    const update = () => {
+      const total = document.documentElement.scrollHeight - window.innerHeight;
+      setProgress(total > 0 ? (window.scrollY / total) * 100 : 0);
+    };
+
+    if (window.CSS?.supports("animation-timeline", "scroll()")) {
+      return;
+    }
+
+    update();
+    window.addEventListener("scroll", update, { passive: true });
+    return () => window.removeEventListener("scroll", update);
+  }, []);
+
+  return (
+    <div
+      className="scroll-progress"
+      style={{ width: `${progress}%` }}
+      role="progressbar"
+      aria-valuenow={Math.round(progress)}
+      aria-valuemin={0}
+      aria-valuemax={100}
+    />
+  );
+}