fix(admin): deterministic UTC timestamp formatting to remove hydration mismatch

lib/format.ts

@@ -11,9 +11,34 @@ export function formatBytes(n: number): string {
   return `${v.toFixed(2)} ${units[i]}`;
 }
 
-export function formatDate(s: string | null | undefined): string {
+function pad(n: number): string {
+  return n < 10 ? `0${n}` : `${n}`;
+}
+
+// Deterministic, timezone-independent date+time formatter.
+// Uses UTC getters so the server (UTC) and client (local TZ) render
+// byte-identical text, avoiding React hydration mismatches (error #425).
+// Output format: "YYYY-MM-DD HH:MM UTC".
+export function formatDateTime(s: string | null | undefined): string {
   if (!s) return '—';
   const d = new Date(s);
   if (Number.isNaN(d.getTime())) return '—';
-  return d.toLocaleString();
+  const date = `${d.getUTCFullYear()}-${pad(d.getUTCMonth() + 1)}-${pad(
+    d.getUTCDate(),
+  )}`;
+  const time = `${pad(d.getUTCHours())}:${pad(d.getUTCMinutes())}`;
+  return `${date} ${time} UTC`;
 }
+
+// Date-only deterministic UTC formatter. Output format: "YYYY-MM-DD UTC".
+export function formatDateOnly(s: string | null | undefined): string {
+  if (!s) return '—';
+  const d = new Date(s);
+  if (Number.isNaN(d.getTime())) return '—';
+  return `${d.getUTCFullYear()}-${pad(d.getUTCMonth() + 1)}-${pad(
+    d.getUTCDate(),
+  )} UTC`;
+}
+
+// Backwards-compatible alias: existing call sites render date+time.
+export const formatDate = formatDateTime;