ConfirmDialog trapped focus and closed on Escape but its container was a plain
div, so screen readers did not announce it as a modal dialog. Its text input
also had only a placeholder, giving no persistent accessible name. Add
role=dialog / aria-modal / aria-label / tabindex to the dialog surface and an
aria-label to the textarea.
Relates to #2790
Co-authored-by: Tim Baek <tim@openwebui.com>
