feat: Set up JavaScript testing framework (Vitest + Playwright)

- Created package.json with Vitest and Playwright dependencies
- Configured vitest.config.js with happy-dom environment
- Configured playwright.config.js with Chromium browser
- Created test directory structure (tests/frontend/unit and e2e)
- Added setup.test.js with 10 Vitest validation tests
- Added setup.spec.js with 6 Playwright E2E validation tests
- Created FRONTEND_SETUP.md with Node.js installation guide
- Updated instructions.md marking task complete

Note: Requires Node.js installation before running tests

playwright.config.js

@@ -0,0 +1,88 @@
+import { defineConfig, devices } from '@playwright/test';
+
+/**
+ * Playwright configuration for E2E tests
+ * @see https://playwright.dev/docs/test-configuration
+ */
+export default defineConfig({
+  // Test directory
+  testDir: './tests/frontend/e2e',
+  
+  // Maximum time one test can run for
+  timeout: 30 * 1000,
+  
+  // Run tests in parallel
+  fullyParallel: true,
+  
+  // Fail the build on CI if you accidentally left test.only in the source code
+  forbidOnly: !!process.env.CI,
+  
+  // Retry on CI only
+  retries: process.env.CI ? 2 : 0,
+  
+  // Opt out of parallel tests on CI
+  workers: process.env.CI ? 1 : undefined,
+  
+  // Reporter to use
+  reporter: [
+    ['html', { outputFolder: 'playwright-report' }],
+    ['list']
+  ],
+  
+  // Shared settings for all the projects below
+  use: {
+    // Base URL to use in actions like `await page.goto('/')`
+    baseURL: 'http://127.0.0.1:8000',
+    
+    // Collect trace when retrying the failed test
+    trace: 'on-first-retry',
+    
+    // Screenshot on failure
+    screenshot: 'only-on-failure',
+    
+    // Video on failure
+    video: 'retain-on-failure',
+    
+    // Action timeout
+    actionTimeout: 10 * 1000,
+    
+    // Navigation timeout
+    navigationTimeout: 30 * 1000
+  },
+
+  // Configure projects for major browsers
+  projects: [
+    {
+      name: 'chromium',
+      use: { ...devices['Desktop Chrome'] },
+    },
+    
+    // Uncomment for cross-browser testing
+    // {
+    //   name: 'firefox',
+    //   use: { ...devices['Desktop Firefox'] },
+    // },
+    // {
+    //   name: 'webkit',
+    //   use: { ...devices['Desktop Safari'] },
+    // },
+    
+    // Mobile viewports
+    // {
+    //   name: 'Mobile Chrome',
+    //   use: { ...devices['Pixel 5'] },
+    // },
+    // {
+    //   name: 'Mobile Safari',
+    //   use: { ...devices['iPhone 12'] },
+    // },
+  ],
+
+  // Run your local dev server before starting the tests
+  webServer: {
+    command: 'conda run -n AniWorld python -m uvicorn src.server.fastapi_app:app --host 127.0.0.1 --port 8000',
+    url: 'http://127.0.0.1:8000',
+    reuseExistingServer: !process.env.CI,
+    timeout: 120 * 1000,
+  },
+});