Properly calculate page height to avoid scrolling behavior

[flowln]

In both spu-ui and in qua-ui, the available height seems to be calculated slightly incorrectly, leading to them having a scrolling layout that can hide part of the application. This is more noticeable on qua-ui:

Ideally, the page should not scroll, and all widgets should fit neatly on the available space, using scrolling frames only when actually intended.