feat: add 'Don't show this warning again' to cloud connection failure dialog

The "Failed to connect to the cloud device server" dialog previously
reappeared every time the MQTT connection failed, which was disruptive
for users on LAN-only or offline setups.

Replace MessageDialog with RichMessageDialog and add a
"Don't show this warning again" checkbox.  When checked, the config key
suppress_cloud_warnings is set to "1" and the dialog is permanently
suppressed for future sessions.

Closes #10589

Author: BenJule

src/slic3r/GUI/GUI_App.cpp

@@ -2061,10 +2061,14 @@ void GUI_App::init_networking_callbacks()
                 GUI::wxGetApp().CallAfter([this] {
                     static bool is_showing = false;
                     if (is_showing) return;
+                    if (app_config && app_config->get("suppress_cloud_warnings") == "1") return;
                     is_showing = true;
                     BOOST_LOG_TRIVIAL(trace) << "static: server connection failed";
-                    MessageDialog msg_dlg(nullptr, _L("Failed to connect to the cloud device server. Please check your network and firewall."), "", wxOK);
+                    RichMessageDialog msg_dlg(nullptr, _L("Failed to connect to the cloud device server. Please check your network and firewall."), "", wxOK);
+                    msg_dlg.ShowCheckBox(_L("Don't show this warning again"));
                     msg_dlg.ShowModal();
+                    if (msg_dlg.IsCheckBoxChecked() && app_config)
+                        app_config->set("suppress_cloud_warnings", "1");
                     is_showing = false;
                 });
                 return;