fix(ui): user menu header follows rounded theme corners

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -981,7 +981,7 @@ export const App: React.FC = () => {
             </button>
 
             {showProfileMenu && (
-              <div className="absolute right-0 top-full mt-1.5 w-64 panel-surface shadow-panel z-50 divide-y divide-border text-xs origin-top-right animate-in fade-in zoom-in-95 slide-in-from-top-1 duration-150">
+              <div className="absolute right-0 top-full mt-1.5 w-64 panel-surface shadow-panel overflow-hidden z-50 divide-y divide-border text-xs origin-top-right animate-in fade-in zoom-in-95 slide-in-from-top-1 duration-150">
                 {/* User Info Header */}
                 <div className="p-3 bg-canvas flex items-center gap-2.5">
                   <UserAvatar user={user} size="md" className="border border-border/70" />