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/pages/AttendanceAdmin.tsx

@@ -87,7 +87,7 @@ export default function AttendanceAdmin() {
   useModalLock(showEditModal);
   useModalLock(showCreateModal);
 
-  if (!hasPermission("attendance.admin")) return <Forbidden />;
+  if (!hasPermission("attendance.manage")) return <Forbidden />;
 
   // Show skeleton only on initial load (no data yet), not on filter changes
   const isInitialLoad =