master: 添加会话模块及界面改进

- 新增 ChatView 页面及其逻辑设计
- 修改 App.vue 以支持动态会话标题
- 调整 Sidebar 为固定高度及改进滚动样式
- 优化会话分页，添加 lastPage 逻辑
- 在 SessionSidebar 中实现刷新操作和路由同步
- 更新路由配置，添加 chat 相关路径
- 添加单元测试以覆盖新逻辑

src/router/index.js

@@ -2,6 +2,7 @@ import { createRouter, createWebHistory } from 'vue-router'
 import LoginView from '../views/LoginView.vue'
 import WelcomeView from '../views/WelcomeView.vue'
 import UsersView from '../views/UsersView.vue'
+import ChatView from '../views/ChatView.vue'
 
 const router = createRouter({
   history: createWebHistory(import.meta.env.BASE_URL),
@@ -9,6 +10,7 @@ const router = createRouter({
     { path: '/', name: 'login', component: LoginView },
     { path: '/welcome', name: 'welcome', component: WelcomeView },
     { path: '/users', name: 'users', component: UsersView },
+    { path: '/chat/:id?', name: 'chat', component: ChatView },
     { path: '/:pathMatch(.*)*', redirect: '/' },
   ],
 })