chore: 安装 Playwright + 配置 E2E 基础框架

- 安装 @playwright/test 1.60.0
- 创建 e2e/playwright.config.ts（webServer 自动启动 vite dev）
- 创建 e2e/mocks/ipc.ts（Tauri IPC mock）
- 新增 npm run test:e2e 脚本

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

package.json

@@ -9,7 +9,8 @@
     "lint": "eslint .",
     "preview": "vite preview",
     "test": "vitest run",
-    "test:watch": "vitest"
+    "test:watch": "vitest",
+    "test:e2e": "playwright test --config e2e/playwright.config.ts"
   },
   "dependencies": {
     "@tailwindcss/vite": "^4.3.0",
@@ -25,6 +26,7 @@
   },
   "devDependencies": {
     "@eslint/js": "^10.0.1",
+    "@playwright/test": "^1.60.0",
     "@tauri-apps/cli": "^2.11.2",
     "@types/node": "^24.12.3",
     "@types/react": "^19.2.14",