feat: auto-populate department_id on create + seed default campus with backfill

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

@@ -36,8 +36,13 @@ export class AttendanceService {
       throw new BadRequestException('records array must not be empty');
     }
 
-    const entities = dto.records.map((r) =>
-      this.attendanceRepo.create({
+    // Batch-load student departmentIds
+    const ids = [...new Set(dto.records.map((r) => r.studentId))];
+    const students = await this.studentRepo.find({ where: { id: In(ids) } });
+    const deptMap = new Map(students.map((s) => [s.id, s.departmentId]));
+
+    const entities = dto.records.map((r) => {
+      const entity = this.attendanceRepo.create({
         studentId: r.studentId,
         classId: r.classId ?? undefined,
         attendanceDate: r.attendanceDate,
@@ -45,8 +50,10 @@ export class AttendanceService {
         status: r.status,
         remark: r.remark,
         source: r.source || 'manual',
-      }),
-    );
+      });
+      entity.departmentId = deptMap.get(r.studentId)!;
+      return entity;
+    });
 
     const saved = await this.attendanceRepo.save(entities);
     return { count: saved.length, records: saved };