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/servers/display-server/Cargo.toml

@@ -9,6 +9,7 @@ server-framework = { workspace = true }
 libkos = { workspace = true }
 port-framebuffer = { workspace = true }
 raster = { workspace = true }
+theme = { workspace = true }
 
 [dev-dependencies]
 driver-framebuffer-mock = { workspace = true }