[Feature request] Different theme on a workspace bases

**Is your feature request related to a problem? Please describe.**
My problem is I have 3 identical workspaces pointing to different environments (local, test, dev, prod..) and it happen from time to time that I send requests to an env without realizing I'm using the wrong workspace.

**Describe the solution you'd like**
It would be nice to have a clear visual indication of what workspace I'm using, be side the label on the top left corner. I thought about per workspaces theme, something like have a light theme for prod and a dark one for dev but any clear indicator would do, something more visible then the little label in the left, something that struck at first sight and my mind can process without even thinking about it.

The issue names only the workspace label in the top-left corner, not any files or tests. Start by tracing how that label and workspace identity are rendered in the desktop UI, then review existing theme behavior. Done means users can immediately distinguish local, test, dev, and prod workspaces through a clear visual indicator.

Written by the indexing model from the issue text.