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

backend/cmd/main.go

@@ -300,11 +300,18 @@ func handleS2AProxy(w http.ResponseWriter, r *http.Request) {
 	}
 	defer resp.Body.Close()
 
-	// 记录响应状态
+	// 读取响应体
-	if resp.StatusCode != 200 {
+	bodyBytes, err := io.ReadAll(resp.Body)
-		logger.Warning(fmt.Sprintf("S2A 返回 %d", resp.StatusCode), "", "proxy")
+	if err != nil {
+		logger.Error(fmt.Sprintf("读取响应失败: %v", err), "", "proxy")
+		api.Error(w, http.StatusBadGateway, "读取响应失败")
+		return
 	}
 
+	// 记录响应状态和内容摘要
+	logger.Info(fmt.Sprintf("S2A 响应: status=%d, len=%d, body=%s",
+		resp.StatusCode, len(bodyBytes), string(bodyBytes[:min(200, len(bodyBytes))])), "", "proxy")
+
 	// 复制响应头
 	for key, values := range resp.Header {
 		for _, value := range values {
@@ -314,7 +321,7 @@ func handleS2AProxy(w http.ResponseWriter, r *http.Request) {
 
 	// 复制响应状态和内容
 	w.WriteHeader(resp.StatusCode)
-	io.Copy(w, resp.Body)
+	w.Write(bodyBytes)
 }
 
 func handleMailServices(w http.ResponseWriter, r *http.Request) {

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)