The main dropdown menu component that manages state and positioning.
:id - Required unique identifier for the dropdown menu. :open - Whether the dropdown is initially open. Defaults to false. :use-portal - Whether to render the dropdown in a portal. Defaults to false. :portal-container - CSS selector for the portal container. Defaults to nil. :on-open - Handler for dropdown menu open event. :on-close - Handler for dropdown menu close event. :class - Additional CSS classes.