style(ui): use padding for AuthDivider vertical spacing (#446)

Switch my-8 to py-8 on AuthDivider so vertical spacing is internal
padding, not affected by the parent space-y-0 override on the login
page which was suppressing the top margin.

Fixes #446

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/ui/src/components/AuthSurface.tsx

@@ -153,7 +153,7 @@ export function AuthDivider({
   return (
     <div
       className={joinClassNames(
-        "my-8 flex items-center gap-3 text-[0.67rem] font-semibold uppercase tracking-[0.08em] text-[#5a6a87] dark:text-[#8f9db7]",
+        "py-8 flex items-center gap-3 text-[0.67rem] font-semibold uppercase tracking-[0.08em] text-[#5a6a87] dark:text-[#8f9db7]",
         className
       )}
     >