fix(backend): improve captcha validation and forward service sync

- Add cloudflare site/secret key validation for captcha enabled check
- Fix forward create to use UpdateService with tolerateExists for idempotent sync
- Introduce isAlreadyExistsMessage helper excluding address-in-use errors
- Add contract tests for forward toggle, address-in-use rollback, captcha compatibility

go-backend/internal/http/handler/control_plane.go

@@ -311,7 +311,7 @@ func (h *Handler) sendNodeCommand(nodeID int64, commandType string, data interfa
 	}
 	msg := strings.ToLower(strings.TrimSpace(err.Error()))
 	if tolerateExists {
-		if strings.Contains(msg, "exists") || strings.Contains(msg, "already") || strings.Contains(msg, "已存在") {
+		if isAlreadyExistsMessage(msg) {
 			return result, nil
 		}
 	}
@@ -907,6 +907,17 @@ func isNotFoundError(err error) bool {
 	return strings.Contains(msg, "not found") || strings.Contains(msg, "不存在")
 }
 
+func isAlreadyExistsMessage(message string) bool {
+	msg := strings.ToLower(strings.TrimSpace(message))
+	if msg == "" {
+		return false
+	}
+	if strings.Contains(msg, "address already in use") {
+		return false
+	}
+	return strings.Contains(msg, "already exists") || strings.Contains(msg, "已存在")
+}
+
 func buildForwardServiceConfigs(baseName string, forward *forwardRecord, tunnel *tunnelRecord, node *nodeRecord, port int, limiterID *int64, tunnelTLSProtocol bool) []map[string]interface{} {
 	protocols := []string{"tcp", "udp"}
 	services := make([]map[string]interface{}, 0, 2)

go-backend/internal/http/handler/control_plane_test.go

@@ -53,3 +53,15 @@ func TestShouldTryLegacySingleService(t *testing.T) {
 		t.Fatalf("DeleteService should not require legacy fallback")
 	}
 }
+
+func TestIsAlreadyExistsMessage(t *testing.T) {
+	if !isAlreadyExistsMessage("service demo already exists") {
+		t.Fatalf("expected already exists message to be tolerated")
+	}
+	if !isAlreadyExistsMessage("服务已存在") {
+		t.Fatalf("expected Chinese already exists message to be tolerated")
+	}
+	if isAlreadyExistsMessage("listen tcp [::]:10001: bind: address already in use") {
+		t.Fatalf("address already in use must not be treated as already exists")
+	}
+}

go-backend/internal/http/handler/handler.go

@@ -989,10 +989,27 @@ func (h *Handler) captchaEnabled() (bool, error) {
 	if err != nil {
 		return false, err
 	}
-	if cfg == nil {
+	if cfg == nil || !strings.EqualFold(strings.TrimSpace(cfg.Value), "true") {
 		return false, nil
 	}
-	return strings.EqualFold(cfg.Value, "true"), nil
+
+	siteCfg, err := h.repo.GetConfigByName("cloudflare_site_key")
+	if err != nil {
+		return false, err
+	}
+	if siteCfg == nil || strings.TrimSpace(siteCfg.Value) == "" {
+		return false, nil
+	}
+
+	secretCfg, err := h.repo.GetConfigByName("cloudflare_secret_key")
+	if err != nil {
+		return false, err
+	}
+	if secretCfg == nil || strings.TrimSpace(secretCfg.Value) == "" {
+		return false, nil
+	}
+
+	return true, nil
 }
 
 func (h *Handler) apiClientCaptchaBypassEnabled(r *http.Request) bool {

go-backend/internal/http/handler/mutations.go

@@ -1183,7 +1183,7 @@ func (h *Handler) forwardCreate(w http.ResponseWriter, r *http.Request) {
 		response.WriteJSON(w, response.Err(-2, err.Error()))
 		return
 	}
-	if err := h.syncForwardServices(createdForward, "AddService", false); err != nil {
+	if err := h.syncForwardServices(createdForward, "UpdateService", true); err != nil {
 		_ = h.deleteForwardByID(forwardID)
 		response.WriteJSON(w, response.ErrDefault(err.Error()))
 		return