feat(frontend): S0 Vue3 脚手架 + auth + Layout shell（4入口，模拟/实盘灰显）

- Vite+TS+ElementPlus+ECharts+Pinia+Router+Axios
- auth store + JWT axios 拦截器 + 路由守卫
- 登录页 + Layout（侧栏 4 入口，回测/投研 active，模拟/实盘 disabled）
- 占位页（backtest/factor，S1/S2 填充）
- vitest auth store 3 tests passed + build 通过(dist 生成)

frontend/package.json

@@ -0,0 +1,30 @@
+{
+  "name": "frontend",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vue-tsc -b && vite build",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "axios": "^1.18.1",
+    "echarts": "^6.1.0",
+    "element-plus": "^2.14.2",
+    "pinia": "^3.0.4",
+    "vue": "^3.5.39",
+    "vue-router": "^5.1.0"
+  },
+  "devDependencies": {
+    "@types/node": "^24.13.2",
+    "@vitejs/plugin-vue": "^6.0.7",
+    "@vue/test-utils": "^2.4.11",
+    "@vue/tsconfig": "^0.9.1",
+    "jsdom": "^29.1.1",
+    "typescript": "~6.0.2",
+    "vite": "^8.1.1",
+    "vitest": "^4.1.10",
+    "vue-tsc": "^3.3.5"
+  }
+}