upd: tambah notifikasi success/error saat simpan Settings

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

src/frontend/routes/dev.tsx

@@ -70,6 +70,7 @@ import {
   TbUserSearch,
   TbUsers,
 } from 'react-icons/tb'
+import { notifications } from '@mantine/notifications'
 import { type Role, useLogout, useSession } from '@/frontend/hooks/useAuth'
 import { usePresence } from '@/frontend/hooks/usePresence'
 
@@ -1517,6 +1518,10 @@ function SettingsPanel() {
       qc.invalidateQueries({ queryKey: ['admin', 'config'] })
       setSaved(true)
       setTimeout(() => setSaved(false), 2000)
+      notifications.show({ color: 'green', title: 'Tersimpan', message: 'Konfigurasi berhasil disimpan.' })
+    },
+    onError: () => {
+      notifications.show({ color: 'red', title: 'Gagal', message: 'Terjadi kesalahan saat menyimpan konfigurasi.' })
     },
   })