Need an easier way to refresh a custom registry

[danbarr]

Currently, the desktop app only seems to refresh the registry when you save it in the settings. But upstream registries change over time, and certainly will in the case of the ToolHive Registry Server and auto-discovery of workloads running in K8s.

Without an easy refresh mechanism, users may be operating off outdated information.

I think two things are needed:

1. A periodic background refresh of the remote registry, with a sensible default (15 minutes?) which is configurable in the settings
2. A "Refresh" button on the Registry page, visible when a non-default registry is configured, and which invalidates the local cache to force a refresh (equivalent to the CLI's thv registry list --refresh flag)