refactor: update icon usage to use mdi imports for consistency

src/views/errors/NotFound.vue

@@ -3,12 +3,13 @@
     :code="404"
     color="info"
     description="你輸入的網址不存在，或頁面已被移除。"
-    icon="mdi-map-marker-question-outline"
+    :icon="mdiMapMarkerQuestionOutline"
     :show-login="false"
     title="找不到頁面"
   />
 </template>
 
 <script setup lang="ts">
+import { mdiMapMarkerQuestionOutline } from '@mdi/js'
 import ErrorShell from './ErrorShell.vue'
 </script>