test(e2e): playwright smoke for create→practice flow

packages/frontend/package.json

@@ -20,6 +20,7 @@
     "zustand": "^4.5.0"
   },
   "devDependencies": {
+    "@playwright/test": "^1.60.0",
     "@testing-library/jest-dom": "^6.5.0",
     "@testing-library/react": "^16.0.0",
     "@types/canvas-confetti": "^1.6.0",

packages/frontend/playwright.config.ts

@@ -0,0 +1,24 @@
+import { defineConfig } from '@playwright/test';
+
+export default defineConfig({
+  testDir: '../../e2e',
+  webServer: [
+    {
+      command:
+        'rm -f data/e2e.db && DB_PATH=./data/e2e.db npm -w @flashcard/backend run db:migrate && DB_PATH=./data/e2e.db npm -w @flashcard/backend run dev',
+      cwd: '../..',
+      port: 3000,
+      reuseExistingServer: false,
+      timeout: 60_000,
+    },
+    {
+      command: 'npm -w @flashcard/frontend run dev',
+      cwd: '../..',
+      port: 5173,
+      reuseExistingServer: false,
+      timeout: 60_000,
+    },
+  ],
+  use: { baseURL: 'http://localhost:5173' },
+  timeout: 30_000,
+});