fix: Add babel configuration for Playwright to handle TypeScript declare fields

- Configure babel plugins for TypeScript with allowDeclareFields option
- Add module resolver for @ alias to src directory
- Create custom babel plugin to stub Vue/CSS imports
- Add browser globals polyfill using happy-dom for Node.js context
- Update playwright.i18n.config.ts with babel configuration

This enables collect-i18n tests to run with proper TypeScript and module transformations.

playwright.i18n.config.ts

@@ -1,6 +1,6 @@
 import { defineConfig } from '@playwright/test'
 
-export default defineConfig({
+const config: any = defineConfig({
   testDir: './scripts',
   use: {
     baseURL: 'http://localhost:5173',
@@ -8,5 +8,40 @@ export default defineConfig({
   },
   reporter: 'list',
   timeout: 60000,
-  testMatch: /collect-i18n-.*\.ts/
+  testMatch: /collect-i18n-.*\.ts/,
+  // Start dev server before running tests
+  webServer: {
+    command: 'pnpm dev',
+    url: 'http://localhost:5173',
+    reuseExistingServer: true,
+    timeout: 60000
+  }
 })
+
+// Configure babel plugins for TypeScript with declare fields and module resolution
+config['@playwright/test'] = {
+  babelPlugins: [
+    // Stub Vue and CSS imports first to prevent parsing errors
+    ['babel-plugin-stub-vue-imports'],
+    // Module resolver to handle @ alias
+    [
+      'babel-plugin-module-resolver',
+      {
+        root: ['./'],
+        alias: {
+          '@': './src'
+        }
+      }
+    ],
+    // Then TypeScript transformation with declare field support
+    [
+      '@babel/plugin-transform-typescript',
+      {
+        allowDeclareFields: true,
+        onlyRemoveTypeImports: true
+      }
+    ]
+  ]
+}
+
+export default config