feat: 部署到服务器+移动端适配+帮助系统RAG集成+网页图标

- 部署脚本 deploy.sh：一键部署到 154.8.162.18，端口3400，Nginx conf.d
- 应用名改为「企业用工专家」（登录/注册/侧边栏/员工端等6处）
- 移动端适配修复：Attendance/Dashboard/Settings/Contracts 6处grid响应式
- 帮助系统：HelpModal 组件 + TopNav 帮助图标 + RAG语义搜索集成
  - 后端 rag.service.ts 新增23条帮助种子数据 + searchHelp()
  - 前端搜索调用 /ai/rag/help-search，RAG不可用时回退关键词匹配
- 网页图标 favicon.svg（indigo主色+建筑人形图案）
- index.html 标题改为「企业用工专家」

frontend/src/components/layout/TopNav.tsx

@@ -1,15 +1,17 @@
 import { Link, useNavigate } from 'react-router-dom'
-import { ChevronDown, Settings as SettingsIcon, Bell, Menu } from 'lucide-react'
+import { ChevronDown, Settings as SettingsIcon, Bell, Menu, HelpCircle } from 'lucide-react'
 import { useState } from 'react'
 import { useQuery } from '@tanstack/react-query'
 import { useAuthStore } from '../../store/authStore'
 import api from '../../lib/api'
 import Breadcrumb from './Breadcrumb'
+import HelpModal from '../HelpModal'
 
 export default function TopNav({ onMenuClick }: { onMenuClick?: () => void }) {
   const navigate = useNavigate()
   const { user, logout } = useAuthStore()
   const [menuOpen, setMenuOpen] = useState(false)
+  const [helpOpen, setHelpOpen] = useState(false)
 
   const { data: dashboardData } = useQuery<any>({
     queryKey: ['dashboard'],
@@ -36,8 +38,16 @@ export default function TopNav({ onMenuClick }: { onMenuClick?: () => void }) {
           <Breadcrumb />
         </div>
 
-        {/* 右侧：通知 + 设置 + 用户菜单 */}
+        {/* 右侧：帮助 + 通知 + 设置 + 用户菜单 */}
         <div className="flex items-center gap-2 shrink-0">
+          <button
+            onClick={() => setHelpOpen(true)}
+            className="p-1.5 rounded-md hover:bg-gray-100"
+            aria-label="帮助"
+          >
+            <HelpCircle className="w-4 h-4 text-gray-600" />
+          </button>
+          <HelpModal open={helpOpen} onClose={() => setHelpOpen(false)} />
           <Link to="/settings" className="p-1.5 rounded-md hover:bg-gray-100" aria-label="设置">
             <SettingsIcon className="w-4 h-4 text-gray-600" />
           </Link>