pages/Network: Show mock panel beneath connected message

We can still show the card when connected. (After all, we put a lot of effort into it...)

Before	After

Also separates both PlaceholderMessages - previously one held state through both State (PropertyChanges) and in the actual item, which wasn't ideal but needed to have only one. Since the "Connected" one now fills the mock panel, it is separated for better code cleanliness and as a requirement to anchor to the card.