Fix import statements

Remove unused or unneeded imports and change imports of luxon APIs to
use the wrapper.

components/Timetable.vue

@@ -122,7 +122,7 @@
 </template>
 
 <script setup lang="ts">
-import { DateTime } from "luxon";
+import { DateTime } from "~/shared/utils/luxon";
 import type { Id } from "~/shared/types/common";
 import { pairs, setEquals } from "~/shared/utils/functions";