refactor: move shared utilities to lib/shared/ sub-packages

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

frontend/src/routes/persons/[id]/PersonCard.svelte

@@ -1,6 +1,6 @@
 <script lang="ts">
 import { m } from '$lib/paraglide/messages.js';
-import { formatLifeDateRange } from '$lib/utils/personLifeDates';
+import { formatLifeDateRange } from '$lib/person/personLifeDates';
 import PersonTypeBadge from '$lib/person/PersonTypeBadge.svelte';
 
 let {