refactor(schedule): dedup formatSendAt into shared formatFriendlyDateTime

ScheduleMessageModal had a local formatSendAt(Date) byte-equivalent to the
tested formatFriendlyDateTime (utils/datetimeInput). Reuse the shared, unit-
tested helper instead of a second copy — identical output. (Also prettier-clean.)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/room/ScheduleMessageModal.tsx

@@ -21,7 +21,13 @@ import { useMatrixClient } from '../../hooks/useMatrixClient';
 import { stopPropagation } from '../../utils/keyboard';
 import { scheduleMessage } from '../../utils/scheduledMessages';
 import { useModalStyle } from '../../hooks/useModalStyle';
-import { toLocalDate, toLocalTime, parseLocalDateTime, pickerInputStyle } from '../../utils/datetimeInput';
+import {
+  toLocalDate,
+  toLocalTime,
+  parseLocalDateTime,
+  pickerInputStyle,
+  formatFriendlyDateTime,
+} from '../../utils/datetimeInput';
 
 interface ScheduleMessageModalProps {
   roomId: string;
@@ -47,25 +53,6 @@ function formatRelativeTime(ms: number): string {
   return 'in less than a minute';
 }
 
-function formatSendAt(sendAt: Date): string {
-  const now = new Date();
-  const isToday =
-    sendAt.getFullYear() === now.getFullYear() &&
-    sendAt.getMonth() === now.getMonth() &&
-    sendAt.getDate() === now.getDate();
-  const tomorrow = new Date(now);
-  tomorrow.setDate(tomorrow.getDate() + 1);
-  const isTomorrow =
-    sendAt.getFullYear() === tomorrow.getFullYear() &&
-    sendAt.getMonth() === tomorrow.getMonth() &&
-    sendAt.getDate() === tomorrow.getDate();
-
-  const timeStr = sendAt.toLocaleTimeString(undefined, { hour: '2-digit', minute: '2-digit' });
-  if (isToday) return `Today at ${timeStr}`;
-  if (isTomorrow) return `Tomorrow at ${timeStr}`;
-  return `${sendAt.toLocaleDateString()} at ${timeStr}`;
-}
-
 export function ScheduleMessageModal({
   roomId,
   initialBody,
@@ -112,7 +99,10 @@ export function ScheduleMessageModal({
       setPreview(null);
       return;
     }
-    setPreview({ label: formatSendAt(sendAt), relative: formatRelativeTime(diffMs) });
+    setPreview({
+      label: formatFriendlyDateTime(sendAt.getTime()),
+      relative: formatRelativeTime(diffMs),
+    });
   }, [getSendAt]);
 
   useEffect(() => {