v1.6.5: fix attendance unique constraint, schema sync, seed script

- Change attendance idx_attendance_user_date from unique to index (allow multiple shifts per day)
- Reset migrations to single baseline init migration
- Add seed script with admin user (admin/admin)
- Update CLAUDE.md with migration workflow documentation
- Various frontend fixes (queries, pages, hooks)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/admin/hooks/useAttendanceAdmin.ts

@@ -1,4 +1,5 @@
 import { useState, useEffect, useCallback, useRef } from "react";
+import { useQueryClient } from "@tanstack/react-query";
 import apiFetch from "../utils/api";
 import {
   calcProjectMinutesTotal,
@@ -461,6 +462,7 @@ function buildPrintHtml(
 // ---------------------------------------------------------------------------
 
 export default function useAttendanceAdmin({ alert }: AlertContext) {
+  const queryClient = useQueryClient();
   // ---- Core state ----
   const [loading, setLoading] = useState(true);
   const [month, setMonth] = useState(() => {
@@ -771,6 +773,7 @@ export default function useAttendanceAdmin({ alert }: AlertContext) {
 
       if (result.success) {
         setShowCreateModal(false);
+        queryClient.invalidateQueries({ queryKey: ["attendance"] });
         await fetchData(false);
         await new Promise((resolve) => setTimeout(resolve, 300));
         alert.success(
@@ -842,6 +845,7 @@ export default function useAttendanceAdmin({ alert }: AlertContext) {
 
       if (result.success) {
         setShowBulkModal(false);
+        queryClient.invalidateQueries({ queryKey: ["attendance"] });
         await fetchData(false);
         await new Promise((resolve) => setTimeout(resolve, 300));
         alert.success(
@@ -976,6 +980,7 @@ export default function useAttendanceAdmin({ alert }: AlertContext) {
 
       if (result.success) {
         setShowEditModal(false);
+        queryClient.invalidateQueries({ queryKey: ["attendance"] });
         await fetchData(false);
         await new Promise((resolve) => setTimeout(resolve, 300));
         alert.success(
@@ -1005,6 +1010,7 @@ export default function useAttendanceAdmin({ alert }: AlertContext) {
 
       if (result.success) {
         setDeleteConfirm({ show: false, record: null });
+        queryClient.invalidateQueries({ queryKey: ["attendance"] });
         await fetchData(false);
         alert.success(
           result.message || result.data?.message || "Záznam smazán",