Fix WebUI greeting for qbittorrent-nox

* Check if WebUI is enabled and print an appropriate message otherwise.
* Print an actual runtime server scheme, address and port.

PR #19696.

src/base/http/server.h

@@ -50,6 +50,7 @@ namespace Http
 
         bool setupHttps(const QByteArray &certificates, const QByteArray &privateKey);
         void disableHttps();
+        bool isHttps() const;
 
     private slots:
         void dropTimedOutConnection();