switch the styles for button primary and secondary

@mxmrtns @Dinkh @deniztoprak

from a design perspective, a primary ui should use an outstanding color, like:

inside neo, we are mostly (only) using the "default" version. meaning: a button should use ui: 'secondary' by default and we need to switch the styling for both themes to match it.

before the client project MVP is done, i won't find time for it, but i wanted to at least create the ticket already, so that this topic does not get lost.