fix(server): 时间戳→业务日期/时间全部统一为中国时区（UTC+8）

此前仅'今天'默认值统一为中国日期，Date→字符串的转换仍是 UTC：
- sync 考勤同步窗口 lastSyncAt 时间戳按 UTC 取日期，凌晨会偏一天
- 考勤导出 punchTime/createdAt 显示 UTC 时间
- normalizeDateOnly 把 ISO datetime 按 UTC 归一化，业务日期少一天
- getCourseClock/getChinaDateParts 用 dayjs.utc(date).add(8h) 隐式转换

统一为 dayjs(date).utcOffset(8)，纯日期字符串运算（shiftDate/addDays/
daysInMonth/nextMonth）保留 dayjs.utc；date-normalization 测试断言
同步更新为北京时间语义。

apps/server/src/attendance/attendance-calendar.service.ts

@@ -76,7 +76,7 @@ export class AttendanceCalendarService {
     const start = new Date(weekStart);
     const end = new Date(start);
     end.setDate(start.getDate() + 6);
-    const endStr = dayjs(end).utc().format('YYYY-MM-DD');
+    const endStr = dayjs(end).utcOffset(8).format('YYYY-MM-DD');
 
     const records = await this.attendanceRepo.find({
       where: {

apps/server/src/attendance/attendance-generation.service.ts

@@ -97,7 +97,7 @@ export class AttendanceGenerationService {
     const entities: AttendanceRecord[] = [];
     const end = new Date(dateTo);
     for (let d = new Date(dateFrom); d <= end; d.setDate(d.getDate() + 1)) {
-      const dateStr = dayjs(d).utc().format('YYYY-MM-DD');
+      const dateStr = dayjs(d).utcOffset(8).format('YYYY-MM-DD');
       const weekDay = d.getDay() === 0 ? 7 : d.getDay();
 
       for (const sched of schedules) {
@@ -158,7 +158,7 @@ export class AttendanceGenerationService {
   }
 
   private getCourseClock(date: Date): { date: string; minutes: number } {
-    const c = dayjs.utc(date).add(8, 'hour');
+    const c = dayjs(date).utcOffset(8);
     return {
       date: c.format('YYYY-MM-DD'),
       minutes: c.hour() * 60 + c.minute(),

apps/server/src/attendance/attendance-import.service.ts

@@ -239,7 +239,7 @@ export class AttendanceImportService {
   }
 
   private formatDate(value: Date): string {
-    return dayjs.utc(value).format('YYYY-MM-DD');
+    return dayjs(value).utcOffset(8).format('YYYY-MM-DD');
   }
 
   /**

apps/server/src/attendance/attendance-leave-sync.service.ts

@@ -153,7 +153,7 @@ export class AttendanceLeaveSyncService {
   }
 
   private formatDate(value: Date): string {
-    return dayjs.utc(value).format('YYYY-MM-DD');
+    return dayjs(value).utcOffset(8).format('YYYY-MM-DD');
   }
 
   private async resolveStudentName(dingUserId: string): Promise<string> {

apps/server/src/attendance/attendance-records.controller.ts

@@ -196,11 +196,11 @@ export class AttendanceRecordsController extends AttendanceControllerBase {
         source: record.source || '',
         punchDevice: record.punchDeviceName || record.punchDeviceId || '',
         punchTime: record.punchTime
-          ? dayjs(record.punchTime).utc().format('YYYY-MM-DD HH:mm:ss')
+          ? dayjs(record.punchTime).utcOffset(8).format('YYYY-MM-DD HH:mm:ss')
           : '',
         remark: record.remark || '',
         createdAt: record.createdAt
-          ? dayjs(record.createdAt).utc().format('YYYY-MM-DD HH:mm:ss')
+          ? dayjs(record.createdAt).utcOffset(8).format('YYYY-MM-DD HH:mm:ss')
           : '',
       });
     }

apps/server/src/attendance/attendance-report.service.ts

@@ -142,7 +142,7 @@ export class AttendanceReportService {
   async getAlerts(days: number = 14, threshold: number = 3, accessibleClassIds?: number[]) {
     const cutoff = new Date();
     cutoff.setDate(cutoff.getDate() - days);
-    const cutoffStr = dayjs(cutoff).utc().format('YYYY-MM-DD');
+    const cutoffStr = dayjs(cutoff).utcOffset(8).format('YYYY-MM-DD');
 
     const qb = this.attendanceRepo
       .createQueryBuilder('a')

apps/server/src/attendance/attendance-settlement.service.ts

@@ -285,7 +285,7 @@ export class AttendanceSettlementService {
 
   private getCourseClock(date: Date): { date: string; weekDay: number; minutes: number } {
     // Asia/Shanghai 无夏令时，固定 UTC+8 与 Intl 时区格式化等价
-    const c = dayjs.utc(date).add(8, 'hour');
+    const c = dayjs(date).utcOffset(8);
     const weekDay = c.day() === 0 ? 7 : c.day();
     return {
       date: c.format('YYYY-MM-DD'),