refactor(ui): rename route /korrespondenz → /briefwechsel

Update all internal links (AppNav, CoCorrespondentsList, goto) to the
new URL. No redirect needed — no production URLs exist yet.

Refs: #179

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

frontend/src/routes/briefwechsel/page.server.spec.ts

@@ -0,0 +1,146 @@
+import { describe, expect, it, vi, beforeEach } from 'vitest';
+import { load } from './+page.server';
+
+vi.mock('$lib/api.server', () => ({ createApiClient: vi.fn() }));
+vi.mock('$lib/errors', () => ({ getErrorMessage: (code: string) => code ?? 'Unknown error' }));
+
+import { createApiClient } from '$lib/api.server';
+
+const writeUser = { groups: [{ permissions: ['WRITE_ALL'] }] };
+const readUser = { groups: [{ permissions: ['READ_ALL'] }] };
+
+function makeUrl(params: Record<string, string> = {}): URL {
+	const url = new URL('http://x/korrespondenz');
+	for (const [k, v] of Object.entries(params)) url.searchParams.set(k, v);
+	return url;
+}
+
+function mockApi(calls: { ok: boolean; data?: unknown; status?: number }[]) {
+	const GET = vi.fn();
+	for (const call of calls) {
+		GET.mockResolvedValueOnce({
+			response: { ok: call.ok, status: call.status ?? (call.ok ? 200 : 500) },
+			data: call.data,
+			error: call.ok ? undefined : { code: 'INTERNAL_ERROR' }
+		});
+	}
+	vi.mocked(createApiClient).mockReturnValue({ GET } as ReturnType<typeof createApiClient>);
+	return GET;
+}
+
+beforeEach(() => vi.clearAllMocks());
+
+// ─── No senderId ──────────────────────────────────────────────────────────────
+
+describe('korrespondenz load — no senderId', () => {
+	it('returns empty documents without calling the conversation endpoint', async () => {
+		const GET = mockApi([]);
+
+		const result = await load({
+			url: makeUrl(),
+			fetch: vi.fn() as unknown as typeof fetch,
+			locals: { user: readUser }
+		});
+
+		expect(result.documents).toEqual([]);
+		expect(GET).not.toHaveBeenCalled();
+	});
+});
+
+// ─── With senderId, no receiverId ────────────────────────────────────────────
+
+describe('korrespondenz load — senderId set, no receiverId', () => {
+	it('calls the conversation endpoint and the sender person endpoint', async () => {
+		const docs = [{ id: 'd1', title: 'Testbrief' }];
+		const GET = mockApi([
+			{ ok: true, data: docs },
+			{ ok: true, data: { firstName: 'Hans', lastName: 'Müller' } }
+		]);
+
+		const result = await load({
+			url: makeUrl({ senderId: 'p1' }),
+			fetch: vi.fn() as unknown as typeof fetch,
+			locals: { user: readUser }
+		});
+
+		expect(result.documents).toEqual(docs);
+		expect(result.initialValues.senderName).toBe('Hans Müller');
+		expect(result.initialValues.receiverName).toBe('');
+		expect(GET).toHaveBeenCalledTimes(2);
+	});
+});
+
+// ─── With senderId and receiverId ────────────────────────────────────────────
+
+describe('korrespondenz load — senderId and receiverId set', () => {
+	it('calls conversation, sender person, and receiver person endpoints', async () => {
+		const GET = mockApi([
+			{ ok: true, data: [] },
+			{ ok: true, data: { firstName: 'Hans', lastName: 'Müller' } },
+			{ ok: true, data: { firstName: 'Anna', lastName: 'Schmidt' } }
+		]);
+
+		const result = await load({
+			url: makeUrl({ senderId: 'p1', receiverId: 'p2' }),
+			fetch: vi.fn() as unknown as typeof fetch,
+			locals: { user: readUser }
+		});
+
+		expect(result.initialValues.senderName).toBe('Hans Müller');
+		expect(result.initialValues.receiverName).toBe('Anna Schmidt');
+		expect(GET).toHaveBeenCalledTimes(3);
+	});
+});
+
+// ─── canWrite derivation ─────────────────────────────────────────────────────
+
+describe('korrespondenz load — canWrite', () => {
+	it('derives canWrite true from WRITE_ALL permission', async () => {
+		mockApi([
+			{ ok: true, data: [] },
+			{ ok: true, data: { firstName: 'Hans', lastName: 'Müller' } }
+		]);
+
+		const result = await load({
+			url: makeUrl({ senderId: 'p1' }),
+			fetch: vi.fn() as unknown as typeof fetch,
+			locals: { user: writeUser }
+		});
+
+		expect(result.canWrite).toBe(true);
+	});
+
+	it('derives canWrite false when user lacks WRITE_ALL', async () => {
+		mockApi([
+			{ ok: true, data: [] },
+			{ ok: true, data: { firstName: 'Hans', lastName: 'Müller' } }
+		]);
+
+		const result = await load({
+			url: makeUrl({ senderId: 'p1' }),
+			fetch: vi.fn() as unknown as typeof fetch,
+			locals: { user: readUser }
+		});
+
+		expect(result.canWrite).toBe(false);
+	});
+});
+
+// ─── Backend error propagation ────────────────────────────────────────────────
+
+describe('korrespondenz load — backend error', () => {
+	it('throws when the conversation endpoint returns non-ok', async () => {
+		mockApi([
+			{ ok: false, status: 500 },
+			{ ok: true, data: { firstName: 'Hans', lastName: 'Müller' } }
+		]);
+
+		await expect(
+			load({
+				url: makeUrl({ senderId: 'p1' }),
+				fetch: vi.fn() as unknown as typeof fetch,
+				locals: { user: readUser }
+			})
+		).rejects.toMatchObject({ status: 500 });
+	});
+});