Upgrade proxies from the Servers page

The Servers page now shows when a proxy has an update available. Open its update dialog to compare the installed and latest versions, enable upgrades for that server if needed, and start the upgrade from the panel. The dialog shows progress while the proxy applies the new version.

The server must be online and running FlowGuard Proxy v0.3.7 or newer to upgrade remotely. Older versions still need a manual upgrade first.