fix: unique key warning v DashAttendanceToday

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/admin/components/dashboard/DashAttendanceToday.jsx

@@ -13,8 +13,8 @@ export default function DashAttendanceToday({ attendance }) {
         <Link to="/attendance/admin" className="admin-btn admin-btn-primary admin-btn-sm">Detail &rarr;</Link>
       </div>
       <div className="admin-card-body" style={{ padding: 0 }}>
-        {attendance.users.map((u) => (
-          <div key={u.user_id} className="dash-presence-row">
+        {attendance.users.map((u, i) => (
+          <div key={`${u.user_id}-${i}`} className="dash-presence-row">
             <div className={`dash-presence-avatar ${STATUS_DOT_CLASS[u.status]}`}>
               {u.initials || '?'}
             </div>