UI: Distinguish networks by looking at the UI

[stas-sbi]

SV, Wallet and other UIs don't have clear easy to see indication of the network we are operating on. This adds cognitive load to any human operations and increases the chances of making mistakes.

• There should be an easy way to recognize the network we are operating at a glance
• It should be possible to see form a UI screenshot which network it was taken on

[waynecollier-da]

@stas-sbi A resolution for this issue is on the Digital Asset CN Engineering plan.