refactor(server): 日期工具统一迁入 dayjs（utc 插件），移除手写 Intl/padStart 重复实现

apps/server/src/attendance/attendance-time.ts

@@ -1,22 +1,20 @@
+import dayjs from '../common/dayjs';
+
 export function toMinutes(time: string): number {
   const [hour, minute] = time.split(':').map(Number);
   return hour * 60 + minute;
 }
 
 export function getCourseClock(date: Date): { date: string; minutes: number } {
-  const year = date.getFullYear();
-  const month = String(date.getMonth() + 1).padStart(2, '0');
-  const day = String(date.getDate()).padStart(2, '0');
+  const d = dayjs(date);
   return {
-    date: `${year}-${month}-${day}`,
-    minutes: date.getHours() * 60 + date.getMinutes(),
+    date: d.format('YYYY-MM-DD'),
+    minutes: d.hour() * 60 + d.minute(),
   };
 }
 
 export function shiftDate(date: string, days: number): string {
-  const d = new Date(`${date}T00:00:00.000Z`);
-  d.setUTCDate(d.getUTCDate() + days);
-  return d.toISOString().slice(0, 10);
+  return dayjs.utc(`${date}T00:00:00.000Z`).add(days, 'day').format('YYYY-MM-DD');
 }
 
 export function mapLessonScheduleTimeToSession(startTime: string): string {