perf(frontend): code-split heavy components to improve LCP

Switch the inbounds-page modals, login page's theme switch, and the
Persian date picker to defineAsyncComponent. They're not needed on
first paint, so deferring them shrinks the initial bundle and lets
the LCP element render sooner.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/components/DateTimePicker.vue

@@ -1,17 +1,9 @@
 <script setup>
-import { computed } from 'vue';
+import { computed, defineAsyncComponent } from 'vue';
 import dayjs from 'dayjs';
-import PersianDatePicker from 'vue3-persian-datetime-picker';
 import { useDatepicker } from '@/composables/useDatepicker.js';
 
-// Drop-in replacement for <a-date-picker> that swaps to a real Jalali
-// calendar (vue3-persian-datetime-picker, backed by moment-jalaali)
-// when the panel's "Calendar Type" setting is `jalalian`.
-//
-// The v-model contract matches AD-Vue: the parent works with a dayjs
-// object (or null). For the persian picker we serialize to/from the
-// `YYYY-MM-DD HH:mm:ss` string it expects so callers don't need to
-// know which renderer is active.
+const PersianDatePicker = defineAsyncComponent(() => import('vue3-persian-datetime-picker'));
 
 const props = defineProps({
   value: { type: [Object, null], default: null },