Add hour and minute to comment timestamps on issue pages

Comments now show localized date+time (e.g. "Feb 20, 2026, 2:15 PM")
instead of just the date. Added formatDateTime utility to keep the
existing date-only formatDate unchanged for other contexts.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/lib/utils.ts

@@ -17,6 +17,16 @@ export function formatDate(date: Date | string): string {
   });
 }
 
+export function formatDateTime(date: Date | string): string {
+  return new Date(date).toLocaleString("en-US", {
+    month: "short",
+    day: "numeric",
+    year: "numeric",
+    hour: "numeric",
+    minute: "2-digit",
+  });
+}
+
 export function relativeTime(date: Date | string): string {
   const now = Date.now();
   const then = new Date(date).getTime();