refactor(e2e): extract seedBilateralPair fixture + afterAll cleanup

Lifts the three-API-call seeding (create sender, create receiver,
create document) out of briefwechsel-a11y.spec.ts and into a
dedicated fixtures module. The spec now calls seedBilateralPair()
in beforeAll and cleanupBilateralPair() in afterAll so the test
DB doesn't accrue seeded rows across reruns.

Two caveats captured in the helper docstring: the backend has no
person-delete endpoint (only the document is purged), and the
timestamped last names make leftover persons collision-free.

Refs #305
Fixes @saraholt follow-up 1 + 2 from PR round-2 review

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

frontend/e2e/briefwechsel-a11y.spec.ts

@@ -1,8 +1,13 @@
 import AxeBuilder from '@axe-core/playwright';
 import { test, expect } from '@playwright/test';
+import {
+	seedBilateralPair,
+	cleanupBilateralPair,
+	type BilateralPair
+} from './fixtures/bilateral-correspondence';
 
-// Accessibility coverage specifically for the briefwechsel thumbnail-row
-// layout. Seeds two persons + a bilateral document via the API so the page
+// Accessibility coverage for the briefwechsel thumbnail-row layout. Seeds
+// two persons + a bilateral document via the shared fixture so the page
 // reaches the results state (not the hero), then runs axe-core
 // (wcag2a + wcag2aa) across three viewports and two color schemes.
 
@@ -14,33 +19,15 @@ const VIEWPORTS = [
 
 const THEMES = ['light', 'dark'] as const;
 
-let senderId: string;
-let receiverId: string;
+let pair: BilateralPair;
 
 test.describe('Accessibility — /briefwechsel row layout', () => {
 	test.beforeAll(async ({ request }) => {
-		const timestamp = Date.now();
-		const senderRes = await request.post('/api/persons', {
-			data: { firstName: 'A11y', lastName: `Sender-${timestamp}` }
-		});
-		if (!senderRes.ok()) throw new Error(`Create sender failed: ${senderRes.status()}`);
-		senderId = (await senderRes.json()).id;
+		pair = await seedBilateralPair(request, 'A11y');
+	});
 
-		const receiverRes = await request.post('/api/persons', {
-			data: { firstName: 'A11y', lastName: `Receiver-${timestamp}` }
-		});
-		if (!receiverRes.ok()) throw new Error(`Create receiver failed: ${receiverRes.status()}`);
-		receiverId = (await receiverRes.json()).id;
-
-		const docRes = await request.post('/api/documents', {
-			multipart: {
-				title: 'A11y Test Brief',
-				documentDate: '1950-06-15',
-				senderId,
-				receiverIds: receiverId
-			}
-		});
-		if (!docRes.ok()) throw new Error(`Create document failed: ${docRes.status()}`);
+	test.afterAll(async ({ request }) => {
+		await cleanupBilateralPair(request, pair);
 	});
 
 	for (const vp of VIEWPORTS) {
@@ -49,7 +36,7 @@ test.describe('Accessibility — /briefwechsel row layout', () => {
 				await page.setViewportSize({ width: vp.width, height: vp.height });
 				await page.emulateMedia({ colorScheme: theme });
 				await page.goto(
-					`/briefwechsel?senderId=${encodeURIComponent(senderId)}&receiverId=${encodeURIComponent(receiverId)}`
+					`/briefwechsel?senderId=${encodeURIComponent(pair.senderId)}&receiverId=${encodeURIComponent(pair.receiverId)}`
 				);
 				await page.waitForSelector('[data-hydrated]');
 

frontend/e2e/fixtures/bilateral-correspondence.ts

@@ -0,0 +1,62 @@
+import type { APIRequestContext } from '@playwright/test';
+
+/**
+ * Test fixture for the briefwechsel row layout.
+ *
+ * Creates two persons and one document with sender/receiver between them so
+ * that `/briefwechsel?senderId=X&receiverId=Y` navigates straight to the row
+ * state (not the hero). Each seed uses a `Date.now()`-suffixed last name so
+ * parallel runs and reruns never collide.
+ *
+ * The backend does not expose a person-delete endpoint, so only the document
+ * is cleaned up in {@link cleanupBilateralPair}. The two timestamped persons
+ * remain in the DB — acceptable for the test environment, and the unique
+ * suffix means they cannot conflict with later runs.
+ */
+
+export interface BilateralPair {
+	senderId: string;
+	receiverId: string;
+	documentId: string;
+}
+
+export async function seedBilateralPair(
+	request: APIRequestContext,
+	prefix: string
+): Promise<BilateralPair> {
+	const timestamp = Date.now();
+
+	const senderRes = await request.post('/api/persons', {
+		data: { firstName: prefix, lastName: `Sender-${timestamp}` }
+	});
+	if (!senderRes.ok()) throw new Error(`Create sender failed: ${senderRes.status()}`);
+	const senderId = (await senderRes.json()).id as string;
+
+	const receiverRes = await request.post('/api/persons', {
+		data: { firstName: prefix, lastName: `Receiver-${timestamp}` }
+	});
+	if (!receiverRes.ok()) throw new Error(`Create receiver failed: ${receiverRes.status()}`);
+	const receiverId = (await receiverRes.json()).id as string;
+
+	const docRes = await request.post('/api/documents', {
+		multipart: {
+			title: `${prefix} Brief`,
+			documentDate: '1950-06-15',
+			senderId,
+			receiverIds: receiverId
+		}
+	});
+	if (!docRes.ok()) throw new Error(`Create document failed: ${docRes.status()}`);
+	const documentId = (await docRes.json()).id as string;
+
+	return { senderId, receiverId, documentId };
+}
+
+export async function cleanupBilateralPair(
+	request: APIRequestContext,
+	pair: BilateralPair
+): Promise<void> {
+	// Only the document is purged — the backend has no person-delete endpoint
+	// and the timestamped last names make orphaned person rows safe to leave.
+	await request.delete(`/api/documents/${pair.documentId}`);
+}