fix: ignore recipient if no target is set (aider fix)

backend.go

@@ -19,6 +19,11 @@ type Backend struct {
 }
 
 func (bkd *Backend) sendNotification(recipient ConfigRecipient, email ReceivedEmail) error {
+	if recipient.Target == "" {
+		slog.Warn("no target provided for recipient", slog.String("recipient", strings.Join(recipient.Addresses, ",")))
+		return nil
+	}
+
 	urlParams := url.Values{
 		"title": {email.Msg.Header.Get("Subject")},
 	}