refactor: move tag domain components to lib/tag/

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/document/DescriptionSection.svelte

@@ -1,6 +1,6 @@
 <script lang="ts">
 import { onMount } from 'svelte';
-import TagInput, { type Tag } from '$lib/components/TagInput.svelte';
+import TagInput, { type Tag } from '$lib/tag/TagInput.svelte';
 import FieldLabelBadge from './FieldLabelBadge.svelte';
 import { m } from '$lib/paraglide/messages.js';