feat(persons): show merge panel inline on edit page, remove Gefahrenzone accordion

Closes #342. The PersonDangerZone collapsible wrapper is removed; PersonMergePanel
is now rendered directly in the edit page with its own red border (border-red-200),
preserving the {#key person.id} state-reset behaviour and the two-step merge flow.

Fix PersonTypeahead mock to use Svelte 5 functional stub (not Svelte 3/4 $$ internals).

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

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

@@ -15,7 +15,7 @@ let mergeTargetId = $state('');
 let showMergeConfirm = $state(false);
 </script>
 
-<div class="mb-10 overflow-hidden rounded-sm border border-line bg-surface shadow-sm">
+<div class="mb-10 overflow-hidden rounded-sm border border-red-200 bg-surface shadow-sm">
 	<div class="p-6 md:p-8">
 		<h2 class="mb-1 font-serif text-lg text-ink">{m.person_merge_heading()}</h2>
 		<p class="mb-5 font-sans text-sm text-ink-2">

frontend/src/routes/persons/[id]/PersonMergePanel.svelte.spec.ts

@@ -0,0 +1,55 @@
+import { describe, it, expect, vi, afterEach } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import { page } from 'vitest/browser';
+import PersonMergePanel from './PersonMergePanel.svelte';
+
+vi.mock('$app/forms', () => ({ enhance: () => () => {} }));
+vi.mock('$lib/components/PersonTypeahead.svelte', () => ({
+	default: () => null
+}));
+
+afterEach(cleanup);
+
+const makePerson = (overrides = {}) => ({
+	displayName: 'Hans Müller',
+	...overrides
+});
+
+// ─── Danger indicator ────────────────────────────────────────────────────────
+
+describe('PersonMergePanel — danger indicator', () => {
+	it('renders outer container with red border class', () => {
+		const { container } = render(PersonMergePanel, {
+			props: { person: makePerson(), form: null }
+		});
+		const panel = container.firstElementChild as HTMLElement;
+		expect(panel?.classList.contains('border-red-200')).toBe(true);
+	});
+});
+
+// ─── Initial state ────────────────────────────────────────────────────────────
+
+describe('PersonMergePanel — initial state', () => {
+	it('renders merge heading', async () => {
+		render(PersonMergePanel, { props: { person: makePerson(), form: null } });
+		const heading = page.getByRole('heading', { level: 2 });
+		await expect.element(heading).toBeInTheDocument();
+	});
+
+	it('merge button is disabled when no target selected', async () => {
+		render(PersonMergePanel, { props: { person: makePerson(), form: null } });
+		const mergeBtn = page.getByRole('button', { name: /zusammenführen/i });
+		await expect.element(mergeBtn).toBeDisabled();
+	});
+});
+
+// ─── Error state ──────────────────────────────────────────────────────────────
+
+describe('PersonMergePanel — error state', () => {
+	it('renders mergeError when form contains error', async () => {
+		render(PersonMergePanel, {
+			props: { person: makePerson(), form: { mergeError: 'Zielperson nicht gefunden.' } }
+		});
+		await expect.element(page.getByText('Zielperson nicht gefunden.')).toBeInTheDocument();
+	});
+});

frontend/src/routes/persons/[id]/edit/+page.svelte

@@ -5,7 +5,7 @@ import BackButton from '$lib/components/BackButton.svelte';
 import PersonEditForm from './PersonEditForm.svelte';
 import PersonEditSaveBar from './PersonEditSaveBar.svelte';
 import NameHistoryEditCard from './NameHistoryEditCard.svelte';
-import PersonDangerZone from './PersonDangerZone.svelte';
+import PersonMergePanel from '../PersonMergePanel.svelte';
 
 let { data, form } = $props();
 const person = $derived(data.person);
@@ -35,7 +35,9 @@ const person = $derived(data.person);
 
 	<NameHistoryEditCard aliases={data.aliases} canWrite={true} aliasError={form?.aliasError} />
 
-	<PersonDangerZone person={person} form={form} />
+	{#key person.id}
+		<PersonMergePanel person={person} form={form} />
+	{/key}
 
 	<PersonEditSaveBar discardHref="/persons/{person.id}" formId="person-edit-form" />
 </div>

frontend/src/routes/persons/[id]/edit/PersonDangerZone.svelte

@@ -1,44 +0,0 @@
-<script lang="ts">
-import { m } from '$lib/paraglide/messages.js';
-import PersonMergePanel from '../PersonMergePanel.svelte';
-
-let {
-	person,
-	form
-}: {
-	person: { id: string; firstName?: string | null; lastName: string; displayName: string };
-	form?: { mergeError?: string } | null;
-} = $props();
-
-let open = $state(false);
-</script>
-
-<div class="mt-8 overflow-hidden rounded-sm border border-red-200 bg-surface shadow-sm">
-	<button
-		type="button"
-		onclick={() => (open = !open)}
-		class="flex w-full items-center justify-between px-6 py-4 text-left"
-		aria-expanded={open}
-	>
-		<span class="text-sm font-bold tracking-widest text-red-600 uppercase">
-			{m.person_danger_zone_heading()}
-		</span>
-		<svg
-			class="h-4 w-4 text-red-400 transition-transform {open ? 'rotate-180' : ''}"
-			fill="none"
-			stroke="currentColor"
-			viewBox="0 0 24 24"
-			aria-hidden="true"
-		>
-			<path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M19 9l-7 7-7-7" />
-		</svg>
-	</button>
-
-	{#if open}
-		<div class="border-t border-red-100 px-6 py-4">
-			{#key person.id}
-				<PersonMergePanel person={person} form={form} />
-			{/key}
-		</div>
-	{/if}
-</div>