✨(frontend) fix toggle panel button a11y with dynamic label

improves screen sr by updating label and state indication dynamically

Signed-off-by: Cyril <c.gromoff@gmail.com>

src/frontend/apps/impress/src/features/header/components/ButtonTogglePanel.tsx

@@ -12,12 +12,16 @@ export const ButtonTogglePanel = () => {
     <Button
       size="medium"
       onClick={() => togglePanel()}
-      aria-label={t('Open the header menu')}
+      aria-label={t(
+        isPanelOpen ? 'Close the header menu' : 'Open the header menu',
+      )}
+      aria-expanded={isPanelOpen}
       variant="tertiary"
       icon={
         <Icon $withThemeInherited iconName={isPanelOpen ? 'close' : 'menu'} />
       }
       className="--docs--button-toggle-panel"
+      data-testid="header-menu-toggle"
     />
   );
 };