fix: duplicate class

Author: essenmitsosse

app/components/AppHeader.vue

@@ -270,7 +270,7 @@ onKeyStroke(
       <!-- Mobile: Menu button (always visible, click to open menu) -->
       <ButtonBase
         type="button"
-        class="sm:hidden flex"
+        class="sm:hidden"
         :aria-label="$t('nav.open_menu')"
         :aria-expanded="showMobileMenu"
         @click="showMobileMenu = !showMobileMenu"