A new bundled skin driven by the existing jade_bg.png background: deep
green surfaces, jade-green primary accents, and a soft gold secondary
echoing the stone's veins, plus a jade specular-glare + jade-to-gold
sidebar-border effect. SkinManager auto-discovers it (no C++/CMake
changes) and it appears in Settings -> Appearance as "Jade".
The background asset (res/img/backgrounds/texture/jade_bg.png) is a
binary handled separately; until it lands in the repo the skin falls
back to the programmatic gradient on other machines.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>