feat(search): add GroupDivider shared component

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

frontend/src/lib/components/GroupDivider.svelte

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+<script lang="ts">
+let { label }: { label: string } = $props();
+</script>
+
+<div data-testid="group-divider" class="relative flex items-center py-2 text-center">
+	<div class="flex-grow border-t border-line"></div>
+	<span class="mx-4 font-sans text-xs font-bold tracking-widest text-ink/40 uppercase">{label}</span
+	>
+	<div class="flex-grow border-t border-line"></div>
+</div>

frontend/src/lib/components/GroupDivider.svelte.spec.ts

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+import { describe, expect, it, afterEach } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import { page } from 'vitest/browser';
+import GroupDivider from './GroupDivider.svelte';
+
+afterEach(() => cleanup());
+
+describe('GroupDivider', () => {
+	it('renders the label text', async () => {
+		render(GroupDivider, { label: '1938' });
+		await expect.element(page.getByText('1938')).toBeInTheDocument();
+	});
+
+	it('has data-testid="group-divider" on the root element', async () => {
+		render(GroupDivider, { label: 'Test' });
+		await expect.element(page.getByTestId('group-divider')).toBeInTheDocument();
+	});
+
+	it('renders a person name label', async () => {
+		render(GroupDivider, { label: 'Anna Müller' });
+		await expect.element(page.getByText('Anna Müller')).toBeInTheDocument();
+	});
+});