feat(mcp): 添加 MCP 服务器管理功能

- 新增 Server MCP API 路由 (/api/mcp/*)
  - GET /servers - 获取所有服务器状态
  - POST /servers/:name/connect|disconnect|enable|disable
  - GET /tools - 获取所有 MCP 工具
  - GET /config - 获取 MCP 配置

- 新增 UI MCPPanel 组件
  - 显示服务器列表和状态指示灯
  - 支持连接/断开/启用/禁用操作
  - 展开查看服务器配置和工具列表
  - 响应式设计支持移动端

- 集成到 Web 和 Desktop
  - 添加 Plug 图标按钮到工具栏
  - 点击打开 MCP 管理面板

packages/web/src/pages/Chat.tsx

@@ -3,7 +3,7 @@
  */
 
 import { useEffect, useRef } from 'react';
-import { WifiOff, MessageSquare, Settings, FolderOpen, Terminal } from 'lucide-react';
+import { WifiOff, MessageSquare, Settings, FolderOpen, Terminal, Plug } from 'lucide-react';
 import { motion, AnimatePresence } from 'framer-motion';
 import {
   useChat,
@@ -23,6 +23,7 @@ interface ChatPageProps {
   onToggleFileBrowser?: () => void;
   onOpenConfig?: () => void;
   onOpenCommands?: () => void;
+  onOpenMCP?: () => void;
 }
 
 export function ChatPage({
@@ -34,6 +35,7 @@ export function ChatPage({
   onToggleFileBrowser,
   onOpenConfig,
   onOpenCommands,
+  onOpenMCP,
 }: ChatPageProps) {
   const {
     messages,
@@ -128,8 +130,21 @@ export function ChatPage({
           <ConnectionStatus />
 
           {/* 工具栏按钮 */}
-          {(onOpenConfig || onToggleFileBrowser || onOpenCommands) && (
+          {(onOpenConfig || onToggleFileBrowser || onOpenCommands || onOpenMCP) && (
             <div className="flex items-center gap-1.5 border-l border-gray-600 pl-3">
+              {/* MCP 按钮 */}
+              {onOpenMCP && (
+                <motion.button
+                  whileHover={{ scale: 1.1 }}
+                  whileTap={{ scale: 0.9 }}
+                  onClick={onOpenMCP}
+                  className="p-1.5 rounded-lg text-gray-400 hover:text-gray-200 hover:bg-gray-700 transition-colors"
+                  title="MCP Servers"
+                >
+                  <Plug size={20} />
+                </motion.button>
+              )}
+
               {/* 命令按钮 */}
               {onOpenCommands && (
                 <motion.button