Add Playwright E2E tests replacing Cypress with MSW integration

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

tests/e2e/playwright.config.ts

@@ -0,0 +1,27 @@
+// The Lucia project.
+// Copyright 2026-2026 DSP, inc.  All rights reserved.
+// Authors:
+//   imacat.yang@dsp.im (imacat), 2026/03/22
+
+import { defineConfig } from "@playwright/test";
+
+export default defineConfig({
+  testDir: "./specs",
+  timeout: 30000,
+  expect: { timeout: 5000 },
+  use: {
+    baseURL: "http://localhost:4173",
+    viewport: { width: 1280, height: 720 },
+  },
+  projects: [
+    {
+      name: "chromium",
+      use: { browserName: "chromium" },
+    },
+  ],
+  webServer: {
+    command: "npx vite preview --port 4173",
+    port: 4173,
+    reuseExistingServer: true,
+  },
+});