test(frontend): add real-auth Playwright e2e suite

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/e2e/helpers.ts

@@ -0,0 +1,26 @@
+import { expect, type Page } from '@playwright/test';
+
+/** A fresh, unique account per call so tests never collide in the shared test DB. */
+export function uniqueUser() {
+    const id = `${Date.now()}_${Math.random().toString(36).slice(2, 8)}`;
+    return { username: `e2e_${id}`, password: 'password123' };
+}
+
+/**
+ * Registers a brand-new user and logs in via the real /api/auth flow.
+ * `page.request` shares the browser context's cookie jar, so the session
+ * cookie it sets makes subsequent page navigations authenticated.
+ */
+export async function registerAndLogin(page: Page) {
+    const user = uniqueUser();
+    const register = await page.request.post('/api/auth/register', { data: user });
+    expect(register.ok(), 'register should succeed').toBeTruthy();
+    const login = await page.request.post('/api/auth/login', { data: user });
+    expect(login.ok(), 'login should succeed').toBeTruthy();
+    return user;
+}
+
+/** A small in-memory upload fixture (no files on disk needed). */
+export function textFile(name: string) {
+    return { name, mimeType: 'text/plain', buffer: Buffer.from('e2e test content') };
+}