Add disconnected screen

[Wolkenfarmer]

Context

In the prod frontend the debug bar is not accessible and therefore one has no way of knowing that one may have disconnected from the server and should reload the page. Instead one just notices that one cannot interact with the system anymore and thinks it's broken, which it is not

AC

• [ ] If one disconnects, show a screen promtping the user the reload the page
• [ ] Optional: automatically try to reconnect when screen is shown without reloading
• [ ] Optional: Save login credentials locally in the browser and automatically login on reload

[Toni000]

Simply saving the token and using that to reconnect should be a pretty simple solution here