ToolHive does not gracefully handle misconfigured registries.

[dmjb]

Per an internal report:

1. ToolHive will allow you to add a non existent registry without checking.
2. When attempting to perform an operation with a registry which does not exist, the API times out after 10 seconds and returns a 500.

Proposed fixes:

1. Check to see if a registry is reachable on configuration.
2. Use shorter timeouts + more descriptive responses.