refactor: organize desktop vs. mobile into separate folders

js/desktop/src/components/relative-timestamp.tsx

@@ -0,0 +1,22 @@
+import { useEffect, useState } from "react";
+import { formatDistanceToNow } from "@/lib/time-utils";
+
+const TICK_MS = 30_000;
+
+interface RelativeTimestampProps {
+  date: Date;
+}
+
+/**
+ * Displays a relative timestamp (e.g. "5m ago") that auto-refreshes every 30s.
+ */
+export function RelativeTimestamp({ date }: RelativeTimestampProps) {
+  const [, setTick] = useState(0);
+
+  useEffect(() => {
+    const id = setInterval(() => setTick((t) => t + 1), TICK_MS);
+    return () => clearInterval(id);
+  }, []);
+
+  return <>{formatDistanceToNow(date.toISOString())}</>;
+}