Web UI should ERROR if the backend is unresponsive

[benjaminapetersen]

Tested this, if you run via the docker container and the docker container dies, but you continue to edit things in the browser, there is no notification. This may result in lost work.

Options:

• Simply toast or popup an error if, on save, the backend does not respond
• Additionally, the front end could periodically call a backend health endpoint to verify responsiveness. If there is an error, disable actions until the backend is restarted and the health endpoint responds again