nice update

client/src/hooks/useCountdown.js

@@ -0,0 +1,24 @@
+import { useEffect, useState } from 'react';
+
+export function useCountdown(endsAt) {
+  const [remaining, setRemaining] = useState(0);
+
+  useEffect(() => {
+    if (!endsAt) {
+      setRemaining(0);
+      return undefined;
+    }
+
+    const tick = () => {
+      const ms = new Date(endsAt).getTime() - Date.now();
+      setRemaining(Math.max(0, Math.ceil(ms / 1000)));
+    };
+    tick();
+    const id = setInterval(tick, 250);
+    return () => clearInterval(id);
+  }, [endsAt]);
+
+  const mm = String(Math.floor(remaining / 60)).padStart(2, '0');
+  const ss = String(remaining % 60).padStart(2, '0');
+  return { remaining, label: `${mm}:${ss}` };
+}