refactor: update icon usage to use mdi imports for consistency

src/views/errors/Maintenance.vue

@@ -3,13 +3,14 @@
     code="MAINTENANCE"
     color="info"
     description="目前系統正在維護，請稍後再試。"
-    icon="mdi-tools"
+    :icon="mdiTools"
     :show-login="false"
     title="系統維護中"
   />
 </template>
 
 <script setup lang="ts">
+import { mdiTools } from '@mdi/js'
 import ErrorShell from './ErrorShell.vue'
 </script>