Improve page loading and theme system
- The sidebar is visible while loading with css
There was an apparent problem when switching pages with the new switcher
- css variables are now used
- Theme color is applied to several buttons and texts
where previously Plan color was used
Affects issues:
- Implements #2357
Sidebar items not being rendered caused the currentTab to be undefined,
until the sidebar is opened, and then currentTab is set - which then
caused a useEffect that closes sidebar to fire.
This lead to the sidebar closing right away on the first click.
To fix this the sidebar item state was moved to navigationHook,
and changing the list of items on a sidebar updates currentTab
at the same time to prevent sidebar rendering setting it again.
