feat: 添加用户注册功能前端页面

- 新增 Signup.vue 注册页面
- 路由添加 /signup 路由
- Login.vue 注册链接跳转到注册页

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/router/index.ts

@@ -1,6 +1,7 @@
 import { createRouter, createWebHistory } from 'vue-router'
 import Dashboard from '@/views/Dashboard.vue'
 import Login from '@/views/Login.vue'
+import Signup from '@/views/Signup.vue'
 import Chat from '@/views/Chat.vue'
 import Agents from '@/views/Agents.vue'
 import Team from '@/views/Team.vue'
@@ -23,6 +24,11 @@ const router = createRouter({
       name: 'login',
       component: Login
     },
+    {
+      path: '/signup',
+      name: 'signup',
+      component: Signup
+    },
     {
       path: '/dashboard',
       name: 'dashboard',