fix(hysteria2): emit https server_url for sing-box realm outbound (#9642)

sing-box requires realm.server_url as a full URL (https://host:port).
Bare host:port caused "missing host in realm server_url" on import.
Also forward stun_servers and clear ResolveRealm success message.

Fixes #9635

v2rayN/ServiceLib/Models/Dto/HyRealm.cs

@@ -15,6 +15,15 @@ public record HyRealm(
 {
     public string RendezvousHostPort => RendezvousPort > 0 ? $"{RendezvousHost}:{RendezvousPort}" : RendezvousHost;
 
+    /// <summary>
+    /// sing-box realm.server_url requires a scheme (https:// or http://).
+    /// </summary>
+    public string ToServerUrl()
+    {
+        var scheme = IsHttp ? "http" : "https";
+        return $"{scheme}://{RendezvousHostPort}";
+    }
+
     public static bool TryParse(string? str, out HyRealm? realm)
     {
         realm = null;