[ui polish] Update All Cube Art

[ninavizz]

Update all SD Cube artwork

With SD 1.0.0 the cube was updated to have a more explicit keyhole, and with legibility enhancements to the S and the D. As such, the cubes in all Workstation UIs need updating.

• Client Branding Bar, offline
• Client Branding Bar, online
• Client Login screen
• Dock icon
• Qubes desktop icon (?)

[ninavizz]

^ both of the above dev issues in the client repo, are to complete the art updates in the branding barre and login window. SVG art is in both Issues.

There are not yet any "logged-out/logged-in" states for the branding bar implemented in the client, so that one can just be ignored.