fix: bulk attendance fill — accept string user_ids, skip holidays

- Schema now accepts both string and number user_ids (frontend sends strings)
- Bulk fill now skips Czech public holidays in addition to weekends

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/services/attendance.service.ts

@@ -1,6 +1,6 @@
 import { attendance_leave_type, Prisma } from "@prisma/client";
 import prisma from "../config/database";
-import { getBusinessDaysInMonth } from "../utils/czech-holidays";
+import { getBusinessDaysInMonth, isHoliday } from "../utils/czech-holidays";
 import { localDateStr } from "../utils/date";
 import { getSystemSettings } from "./system-settings";
 
@@ -1087,6 +1087,7 @@ export async function bulkCreateAttendance(data: BulkAttendanceData) {
       const dow = date.getDay();
 
       if (dow === 0 || dow === 6) continue;
+      if (isHoliday(dateStr)) continue;
 
       if (existingSet.has(`${userId}:${dateStr}`)) {
         skipped++;