feat(web): 初始化主页面和监控页面

- 新增 MainView 组件，包含 header、menu 和 page 区域
- 新增 monitor 子页面组件
- 更新路由配置，添加主页面和监控页面路由
- 新增全局样式文件，统一颜色和样式
- 优化 App.vue 样式，移除最小宽高限制

web/src/router/index.js

@@ -3,7 +3,7 @@ import { createRouter, createWebHistory } from 'vue-router'
 const routes = [
   {
     path: '/',
-    redirect: '/login'
+    redirect: '/main'
   },
   {
     path: '/login',
@@ -13,7 +13,14 @@ const routes = [
   {
     path: '/main',
     name: 'main',
-    component: () => import(/* webpackChunkName: "login" */ '@/views/MainView.vue')
+    redirect: '/main/monitor',
+    component: () => import(/* webpackChunkName: "main" */ '@/views/MainView.vue'),
+    children: [
+      {
+        path: 'monitor',
+        component: () => import(/* webpackChunkName: "monitor" */ '@/views/sub/monitor.vue')
+      }
+    ]
   }
 ]