[Bug] input another question during generate result

Hi, I just tried this application, and it is really amazing. However, I also discovered an issue during testing. When entering a prompt, if we need to input multiple lines, we usually use alt + enter to create a new line, but it seems that the application currently doesn't support this well. Additionally, I noticed that when the backend is generating a response, if we continue to input a prompt, it can actually be submitted. This should not be allowed.

Look for the frontend component handling text input and submission, likely in a React component. Find where the 'generate' state is managed and where the submit handler is called. Prevent new line input via alt+enter and disable the input or button while a response is being generated. Test by running the app locally and simulating the described behavior.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.