feat(frontend): wire Vite app to FastAPI parser with NDJSON streaming + Upload page

src/hooks/useCountUp.ts

@@ -0,0 +1,33 @@
+import { useEffect, useRef, useState } from "react";
+
+/**
+ * Animates a numeric value with a smooth ease-out curve.
+ * Zero dependencies, single rAF loop. Re-runs when `value` changes.
+ */
+export function useCountUp(value: number, duration = 850): number {
+  const [n, setN] = useState(0);
+  const displayed = useRef(0);
+  const raf = useRef<number | null>(null);
+
+  useEffect(() => {
+    const from = displayed.current;
+    const to = value;
+    const start = performance.now();
+    if (raf.current !== null) cancelAnimationFrame(raf.current);
+
+    const tick = (now: number) => {
+      const t = Math.min(1, (now - start) / duration);
+      const e = 1 - Math.pow(1 - t, 3); // easeOutCubic
+      const current = from + (to - from) * e;
+      displayed.current = current;
+      setN(current);
+      if (t < 1) raf.current = requestAnimationFrame(tick);
+    };
+    raf.current = requestAnimationFrame(tick);
+    return () => {
+      if (raf.current !== null) cancelAnimationFrame(raf.current);
+    };
+  }, [value, duration]);
+
+  return n;
+}