feat(design): glass surfaces by role, the static Badge, LinkButton, user pickers on the Combobox (E28 S3d1)

frontend/src/components/ui/BackToTop.tsx

@@ -3,6 +3,7 @@ import { createPortal } from "react-dom";
 import { ArrowUp } from "lucide-react";
 import { useTranslation } from "react-i18next";
 import { Pressable } from "./Pressable";
+import { SURFACE } from "./surfaces";
 
 // A floating "back to top" button that fades in once the current page's scroll container is
 // scrolled past a threshold, and smooth-scrolls it back to the top. Every page scrolls inside a
@@ -56,7 +57,7 @@ export default function BackToTop({ dep, threshold = 600 }: { dep?: unknown; thr
     <Pressable
       align="center"
       onClick={toTop}
-      className={`fixed bottom-5 right-5 z-chrome inline-flex items-center justify-center size-12 rounded-full glass-card glass-hover text-fg hover:text-accent transition-all duration-200 ${
+      className={`fixed bottom-5 right-5 z-chrome inline-flex items-center justify-center size-12 ${SURFACE.floating} glass-hover text-fg hover:text-accent transition-all duration-200 ${
         show ? "opacity-100 translate-y-0" : "opacity-0 translate-y-3 pointer-events-none"
       }`}
     >