fix: 修复6个bug + IoT设备控制增强 + DevTools IoT面板

问题1: 刷新后主对话历史不显示，侧边栏子对话列表为空
  - sessionStore: 修复 setCurrentSessionId 用 Map 去重消息
  - AppLayout: 修复 autoLoadNewSession 逻辑
  - useWebSocket: 修复 setMessages 调用时机

问题2: 切换到次级对话后无法切换回主对话
  - Sidebar: 为删除按钮添加 e.stopPropagation()

问题3&4: IoT设备列表展开导致输入栏消失 + 聊天消息无法滚动
  - IoTStatusBar: 从fixed定位改为inline布局
  - ChatContainer: 重构flex布局，MessageList自动撑满

问题5: AI核心无法操作IoT设备 + 无法设置温度等属性
  - 新增 IoTControlTool (iot_control_tool.go)
  - IoTClient: 新增 ToggleDevice/SetProperty/GetHistory
  - 支持 set_temperature/set_brightness/set_position/set_mode/set_color

问题6: DevTools启动时Gateway代理登录异常
  - devtools: 登录失败时静默降级，不阻塞启动

额外修复:
  - iot_tools.go: 修复fmt.Sprintf参数缺失
  - iot-debug-service: 修复并发死锁问题
  - DevTools: 新增IoT设备控制面板(API代理+前端UI)

frontend/web/src/components/layout/AppLayout.tsx

@@ -35,9 +35,9 @@ export function AppLayout({ children }: AppLayoutProps) {
       )}
 
       {/* 主内容区 */}
-      <div className="flex-1 flex flex-col min-w-0">
+      <div className="flex-1 flex flex-col min-w-0 overflow-hidden">
         {isLoggedIn && <Header onMenuClick={() => setSidebarOpen(!sidebarOpen)} />}
-        <main className="flex-1 overflow-hidden">{children}</main>
+        <main className="flex-1 min-h-0 overflow-hidden">{children}</main>
       </div>
     </div>
   );

frontend/web/src/components/layout/Sidebar.tsx

@@ -9,16 +9,14 @@ interface SidebarProps {
 export function Sidebar({ onClose }: SidebarProps) {
   const {
     sessions,
-    currentSessionId,
     createSession,
     deleteSession,
     setCurrentSession,
   } = useSession();
-  const storeSessions = useSessionStore((s) => s.sessions);
-  const storeCurrentSessionId = useSessionStore((s) => s.currentSessionId);
+  const currentSessionId = useSessionStore((s) => s.currentSessionId);
 
-  const displaySessions = sessions.length > 0 ? sessions : storeSessions;
-  const activeSessionId = currentSessionId || storeCurrentSessionId;
+  const displaySessions = sessions;
+  const activeSessionId = currentSessionId;
 
   const handleNewChat = async () => {
     const session = await createSession();