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

vitest.config.js

@@ -0,0 +1,46 @@
+import path from 'path';
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    // Use happy-dom for faster DOM testing
+    environment: 'happy-dom',
+    
+    // Include test files
+    include: ['tests/frontend/unit/**/*.{test,spec}.{js,mjs,cjs}'],
+    
+    // Global test utilities
+    globals: true,
+    
+    // Coverage configuration
+    coverage: {
+      provider: 'v8',
+      reporter: ['text', 'html', 'json'],
+      reportsDirectory: './htmlcov_frontend',
+      include: ['src/server/web/static/js/**/*.js'],
+      exclude: [
+        'node_modules/',
+        'tests/',
+        '**/*.test.js',
+        '**/*.spec.js'
+      ],
+      all: true,
+      lines: 80,
+      functions: 80,
+      branches: 80,
+      statements: 80
+    },
+    
+    // Test timeout (30 seconds)
+    testTimeout: 30000,
+    
+    // Hook timeout (10 seconds)
+    hookTimeout: 10000
+  },
+  
+  resolve: {
+    alias: {
+      '@': path.resolve(__dirname, './src/server/web/static/js')
+    }
+  }
+});