Add Playwright E2E tests replacing Cypress with MSW integration

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

tests/e2e/helpers.ts

@@ -0,0 +1,30 @@
+// The Lucia project.
+// Copyright 2026-2026 DSP, inc.  All rights reserved.
+// Authors:
+//   imacat.yang@dsp.im (imacat), 2026/03/22
+
+import { type BrowserContext } from "@playwright/test";
+
+/**
+ * Sets authentication cookies to simulate a logged-in user.
+ * MSW handles all API interception via the service worker.
+ * @param context - Playwright browser context.
+ */
+export async function loginWithMSW(
+  context: BrowserContext,
+): Promise<void> {
+  await context.addCookies([
+    {
+      name: "luciaToken",
+      value: "fake-access-token-for-testing",
+      domain: "localhost",
+      path: "/",
+    },
+    {
+      name: "isLuciaLoggedIn",
+      value: "true",
+      domain: "localhost",
+      path: "/",
+    },
+  ]);
+}