feat: implement initial backend API server and frontend configuration context for the application.

frontend/src/context/ConfigContext.tsx

@@ -55,7 +55,7 @@ export function ConfigProvider({ children }: { children: ReactNode }) {
     refreshConfig()
   }, [refreshConfig])
 
-  // Update S2A client when config changes
+  // Update S2A client when config changes and auto-test connection
   useEffect(() => {
     if (config.s2a.apiBase && config.s2a.adminKey) {
       const client = new S2AClient({
@@ -63,6 +63,16 @@ export function ConfigProvider({ children }: { children: ReactNode }) {
         apiKey: config.s2a.adminKey,
       })
       setS2aClient(client)
+
+      // 自动测试连接
+      fetch('/api/s2a/test')
+        .then(res => res.json())
+        .then(data => {
+          setIsConnected(data.code === 0)
+        })
+        .catch(() => {
+          setIsConnected(false)
+        })
     } else {
       setS2aClient(null)
       setIsConnected(false)