feat(proxy): add modify proxy API endpoint and functionality

Implement proxy modification feature including:
- New modifyFrpcProxy function in config.go
- New ModifyProxyHandler in frpcProxyAct.go
- New API endpoint in router.go
- Updated API documentation in docs/api.md

frpcProxyAct.go

@@ -107,6 +107,101 @@ func CreateProxyHandler(w http.ResponseWriter, r *http.Request) {
 	postLog.Info(fmt.Sprintf("[CreateProxyHandler] Proxy %s created successfully for instance %d", proxyInfo.Name, instance.ID))
 }
 
+func ModifyProxyHandler(w http.ResponseWriter, r *http.Request) {
+	userID, err := Auth(w, r, http.MethodPost, "superuser", "admin")
+	if err != nil {
+		SendErrorResponse(w, http.StatusUnauthorized, err.Error())
+		postLog.Warning(fmt.Sprintf("[ModifyProxyHandler] Auth failed: %v", err))
+		return
+	}
+
+	body, err := io.ReadAll(r.Body)
+	if err != nil {
+		postLog.Error(fmt.Sprintf("[ModifyProxyHandler] Failed to read request body: %v", err))
+		SendErrorResponse(w, http.StatusBadRequest, "Failed to read request body")
+		return
+	}
+	defer r.Body.Close()
+
+	var reqMap map[string]interface{}
+	if err := json.Unmarshal(body, &reqMap); err != nil {
+		postLog.Error(fmt.Sprintf("[ModifyProxyHandler] Failed to unmarshal request body: %v", err))
+		SendErrorResponse(w, http.StatusBadRequest, "Invalid request format")
+		return
+	}
+
+	instanceID := getStringFromMap(reqMap, "instanceID")
+	if instanceID == "" {
+		postLog.Error("[ModifyProxyHandler] instanceID is required")
+		SendErrorResponse(w, http.StatusBadRequest, "instanceID is required")
+		return
+	}
+
+	proxyInfoMap, ok := reqMap["proxyInfo"].(map[string]interface{})
+	if !ok {
+		postLog.Error("[ModifyProxyHandler] Invalid proxyInfo format")
+		SendErrorResponse(w, http.StatusBadRequest, "Invalid proxyInfo format")
+		return
+	}
+
+	proxyInfo := FrpcProxyInfo{
+		Name:       getStringFromMap(proxyInfoMap, "name"),
+		Type:       getStringFromMap(proxyInfoMap, "type"),
+		LocalIP:    getStringFromMap(proxyInfoMap, "localIP"),
+		LocalPort:  getStringFromMap(proxyInfoMap, "localPort"),
+		RemotePort: getStringFromMap(proxyInfoMap, "remotePort"),
+	}
+
+	if proxyInfo.Name == "" || proxyInfo.Type == "" || proxyInfo.LocalIP == "" ||
+		proxyInfo.LocalPort == "" || proxyInfo.RemotePort == "" {
+		postLog.Error("[ModifyProxyHandler] Missing required fields in proxyInfo")
+		SendErrorResponse(w, http.StatusBadRequest, "Missing required fields in proxyInfo")
+		return
+	}
+
+	var instance FrpcInstance
+	instanceIDInt, _ := strconv.Atoi(instanceID)
+	instance, err = DBQueryFrpcInstanceByID(instanceIDInt)
+	if err != nil {
+		postLog.Error(fmt.Sprintf("[ModifyProxyHandler] Failed to query instance: %v", err))
+		SendErrorResponse(w, http.StatusInternalServerError, "Failed to query instance")
+		return
+	}
+
+	if instance.UserID != userID {
+		postLog.Error(fmt.Sprintf("[ModifyProxyHandler] Instance not found for user %d", userID))
+		SendErrorResponse(w, http.StatusNotFound, "Instance not found")
+		return
+	}
+
+	configContent, err := os.ReadFile(instance.ConfigPath)
+	if err != nil {
+		postLog.Error(fmt.Sprintf("[ModifyProxyHandler] Failed to read config file %s: %v", instance.ConfigPath, err))
+		SendErrorResponse(w, http.StatusInternalServerError, "Failed to read config file")
+		return
+	}
+
+	updatedContent, err := modifyFrpcProxy(string(configContent), proxyInfo)
+	if err != nil {
+		postLog.Error(fmt.Sprintf("[ModifyProxyHandler] Failed to modify proxy: %v", err))
+		SendErrorResponse(w, http.StatusInternalServerError, "Failed to modify proxy")
+		return
+	}
+
+	if err := os.WriteFile(instance.ConfigPath, []byte(updatedContent), 0644); err != nil {
+		postLog.Error(fmt.Sprintf("[ModifyProxyHandler] Failed to write config file %s: %v", instance.ConfigPath, err))
+		SendErrorResponse(w, http.StatusInternalServerError, "Failed to write config file")
+		return
+	}
+
+	SendSuccessResponse(w, "Proxy modified successfully", map[string]interface{}{
+		"instanceID": instance.ID,
+		"configPath": instance.ConfigPath,
+		"proxyName":  proxyInfo.Name,
+	})
+	postLog.Info(fmt.Sprintf("[ModifyProxyHandler] Proxy %s modified successfully for instance %d", proxyInfo.Name, instance.ID))
+}
+
 func DeleteProxyHandler(w http.ResponseWriter, r *http.Request) {
 	userID, err := Auth(w, r, http.MethodPost, "superuser", "admin")
 	if err != nil {