fix(ssr): avoid accessing localStorage during SSR initialization

- Initialize activeInterconnectNodeId with empty string
- Read from localStorage only in client-side
- Defer selected state initialization in NodeSwitcher to useEffect

web/src/api/index.ts

@@ -65,8 +65,16 @@ export interface MonitorStats {
     }[]
   }
 }
-export let activeInterconnectNodeId = localStorage.getItem('activeInterconnectNodeId') || ''
-export let activeInterconnectNodeName = localStorage.getItem('activeInterconnectNodeName') || ''
+
+// 初始化时使用空字符串，避免 SSR 时访问 localStorage
+export let activeInterconnectNodeId = ''
+export let activeInterconnectNodeName = ''
+
+// 在客户端初始化时从 localStorage 读取
+if (typeof window !== 'undefined') {
+  activeInterconnectNodeId = localStorage.getItem('activeInterconnectNodeId') || ''
+  activeInterconnectNodeName = localStorage.getItem('activeInterconnectNodeName') || ''
+}
 
 export function setActiveInterconnectNodeId(id: string, name?: string) {
   activeInterconnectNodeId = id