Offline mode page

[rabbitholiness]

This PR adds a dedicated page that documents the behaviour of the application if the user is offline. You can check out the Figma file here.

[GBKS]

Nice addition. I am not 100% convinced yet that this static banner is the way to go. Do we really need to be in people's face like this? I don't think other applications are that explicit? Might it be enough that the node icon shows a disabled/offline state?

Instead of PSBT in the button label, we should use File.

[rabbitholiness]

I am not 100% convinced yet that this static banner is the way to go. Do we really need to be in people's face like this? I don't think other applications are that explicit?

Fair point. I wouldn't display it through the whole app. But on certain screens I think it's not a bad idea to be a bit more explicit. If you're offline can significantly impact what you see on the activity page, for example. In such cases, I think it can make sense to display something on the page itself. Could be less visually prominent, of course. It could also be some element, like a toast or tooltip, that disappears after a while.