UI touch ups

docker-compose.yml

@@ -7,6 +7,7 @@ services:
       args:
         # Build-time toggle for service worker registration in the generated static HTML.
         PUBLIC_ENABLE_SW: ${PUBLIC_ENABLE_SW:-true}
+        PUBLIC_ENABLE_NAV_HOVER_LINE: ${PUBLIC_ENABLE_NAV_HOVER_LINE:-true}
         PUBLIC_ASSET_VERSION: ${PUBLIC_ASSET_VERSION:-}
         # Public, build-time config baked into the HTML.
         PUBLIC_SITE_URL: ${PUBLIC_SITE_URL:-}