The previous layout nested two scroll regions, sidebar and main, each
with its own scrollbar. Combined with the fixed 100vh flex container,
any child overflow (notably the sidebar nav) spilled past bg-level-0
and exposed the browser's default white background -- most visible in
dark mode as a white strip at the bottom of the viewport.
Switch to a single page-level scroll: pin the header with fixed, let
the wrapper grow with min-h-screen, and drop main's internal overflow.
The drawer becomes fixed too so it stays pinned while the page scrolls
and gets an opaque background to cover scrolled content behind it.
Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>
8fb688f19c