Adjust toolbar transparency and page background image on dark theme

www/assets/css/app.css

@@ -13,7 +13,7 @@ file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 .dark, .theme-dark {
     --theme-background-color: black;
-    --translucent-color: rgba(0,0,0,0.5);
+    --translucent-color: rgba(0,0,0,0.8);
     --solid-translucent-color: black;
     --background-image: url(../images/background-transparent.svg);
 }