refactor: add theme container & lift the dark/light class scope to root & restore scrollbar style.

src/main/frontend/components/theme.cljs

@@ -0,0 +1,12 @@
+(ns frontend.components.theme
+  (:require [rum.core :as rum]))
+
+(rum/defc container
+  [{:keys [theme on-click] :as props} child]
+  (rum/use-effect! #(-> js/document.documentElement
+                        (.setAttribute "data-theme" theme))
+                   [theme])
+  [:div
+   {:class (str theme "-theme")
+    :on-click on-click}
+   child])