Apply Timeout to HttpClient instances created with authentication (#1277)

When AddAuthentication() is called, GxHttpClient passes a non-empty
authCollection to GetHttpClientInstance, so CacheableInstance returns
false and the non-cached branch builds a fresh HttpClient. That branch
never set client.Timeout, leaving the default 100s and silently
ignoring the user-configured Timeout property.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
(cherry picked from commit bb1a5c6)

# Conflicts:
#	dotnet/src/dotnetframework/GxClasses/Domain/GxHttpClient.cs

Author: claudiamurialdo

dotnet/src/dotnetframework/GxClasses/Domain/GxHttpClient.cs

@@ -160,9 +160,9 @@ private async Task<byte[]> ReceiveDataAsync()
 		internal static ConcurrentDictionary<string, HttpClient> _httpClientInstances = new ConcurrentDictionary<string, HttpClient>();
 		private static HttpClient GetHttpClientInstance(Uri URI, int timeout, ArrayList authCollection, ArrayList authProxyCollection, X509Certificate2Collection certificateCollection, List<string> fileCertificateCollection, string proxyHost, int proxyPort, out bool disposableInstance)
 		{
+			HttpClient value;
 			if (CacheableInstance(authCollection, authProxyCollection))
 			{
-				HttpClient value;
 				disposableInstance = false;
 				string key = HttpClientInstanceIdentifier(proxyHost, proxyPort, fileCertificateCollection, timeout);
 				if (_httpClientInstances.TryGetValue(key, out value))
@@ -189,7 +189,9 @@ private static HttpClient GetHttpClientInstance(Uri URI, int timeout, ArrayList
 			else
 			{
 				disposableInstance = true;
-				return new HttpClient(GetHandler(URI, authCollection, authProxyCollection, certificateCollection, proxyHost, proxyPort));
+				value = new HttpClient(GetHandler(URI, authCollection, authProxyCollection, certificateCollection, proxyHost, proxyPort));
+				value.Timeout = TimeSpan.FromMilliseconds(timeout);
+				return value;
 			}
 		}
 
@@ -1024,7 +1026,7 @@ async Task ReadResponseDataAsync()
 				}
 			}
 		}
-		#endif
+#endif
 		bool UseOldHttpClient(string name)
 		{
 			if (Config.GetValueOf("useoldhttpclient", out string useOld) && useOld.StartsWith("y", StringComparison.OrdinalIgnoreCase))