Async Suggestions with Debounce

Instead of filtering a local array, call an API endpoint that returns matching suggestions based on the query. The API call goes in a useEffect that depends on the debounced input value. This shifts the filtering responsibility to the server, enabling fuzzy matching, ranking, and suggestions from a much larger dataset.

Add two new state variables to the autocomplete: isLoading (boolean) for showing a spinner while the fetch is in progress, and error (string or null) for displaying an error message when the fetch fails. These give users feedback about the asynchronous operation rather than leaving them wondering why suggestions are not appearing.