Root cause: the shadcn outline Button variant uses bg-background,
which resolves to the light-theme CSS variable since the admin panel
doesn't wrap itself in a .dark class — so every outline button here
had a white background regardless of border/text color overrides,
making the colored text glare instead of read cleanly. Explicit
bg-zinc-900/hover:bg-zinc-800 on all five outline buttons on this
page (Message, Export, Warn, Un-shadowban, Unban) fixes it.