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/src/router/index.ts

@@ -0,0 +1,30 @@
+import { createRouter, createWebHistory, type RouteRecordRaw } from 'vue-router'
+import { useAuthStore } from '@/stores/auth'
+
+const routes: RouteRecordRaw[] = [
+  { path: '/login', name: 'login', component: () => import('@/views/Login.vue') },
+  {
+    path: '/',
+    component: () => import('@/views/Layout.vue'),
+    children: [
+      { path: '', redirect: '/backtest/new' },
+      { path: 'backtest/new', name: 'bt-new', component: () => import('@/views/backtest/New.vue') },
+      { path: 'backtest/progress/:id', name: 'bt-progress', component: () => import('@/views/backtest/Progress.vue') },
+      { path: 'backtest/result/:id', name: 'bt-result', component: () => import('@/views/backtest/Result.vue') },
+      { path: 'factor/new', name: 'fc-new', component: () => import('@/views/factor/New.vue') },
+      { path: 'factor/result/:id', name: 'fc-result', component: () => import('@/views/factor/Result.vue') },
+    ],
+  },
+]
+
+export const router = createRouter({
+  history: createWebHistory(),
+  routes,
+})
+
+router.beforeEach((to) => {
+  const auth = useAuthStore()
+  if (to.name !== 'login' && !auth.isAuthenticated) {
+    return { name: 'login' }
+  }
+})