refactor: move geschichte domain to lib/geschichte/

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

frontend/src/lib/geschichte/GeschichteEditor.svelte

@@ -5,7 +5,7 @@ import { Editor } from '@tiptap/core';
 import StarterKit from '@tiptap/starter-kit';
 import { m } from '$lib/paraglide/messages.js';
 import type { components } from '$lib/generated/api';
-import PersonMultiSelect from './PersonMultiSelect.svelte';
+import PersonMultiSelect from '$lib/components/PersonMultiSelect.svelte';
 import DocumentMultiSelect from '$lib/document/DocumentMultiSelect.svelte';
 
 type Geschichte = components['schemas']['Geschichte'];