refactor: email template preview modal (#19119)

web/src/lib/modals/EmailTemplatePreviewModal.svelte

@@ -0,0 +1,23 @@
+<script lang="ts">
+  import { Modal, ModalBody } from '@immich/ui';
+  import { t } from 'svelte-i18n';
+
+  interface Props {
+    html: string;
+    onClose: () => void;
+  }
+
+  let { html, onClose }: Props = $props();
+</script>
+
+<Modal title={$t('admin.template_email_preview')} {onClose} size="giant">
+  <ModalBody>
+    <div class="relative w-full h-240 overflow-hidden">
+      <iframe
+        title={$t('admin.template_email_preview')}
+        srcdoc={html}
+        class="absolute top-0 left-0 w-full h-full border-none"
+      ></iframe>
+    </div>
+  </ModalBody>
+</Modal>