feat(theme): themes as files (theme crate: toml subset + ints, contrast check, wire); whimsy dark + light; display reads themes/, serves THEME/THEME_NAME, init SET_THEME -> THEME_CHANGED to all windows, bar themed; k-ui follows; settings appearance; init keeps choice in sealed users/<id>/settings/, reapplies at sign-in + display restart

crates/k-ui/Cargo.toml

@@ -5,6 +5,7 @@ edition = "2024"
 
 [dependencies]
 types = { workspace = true }
+theme = { workspace = true }
 libkos = { workspace = true }
 port-framebuffer = { workspace = true }
 tiny-skia = { version = "0.11", default-features = false, features = ["no-std-float"] }