Review the delineation of sections when contrast themes are applied

[jobara]

Is your feature request related to a problem?

This came up while reviewing #142. There are quite a few horizontal bars appearing towards the top of the page and it is also affecting the presentation of project menu button and its focus styling.

Describe the solution you'd like

Perhaps in some cases there doesn't need to be a clear delineation and just having the negative space between the pieces of content is enough, or using different types of borders including different styles, thicknesses, and etc. Another strategy could be to invert the contrast theme in specific cases, although this should be used sparingly.