Add branching support for chats

[canny]

For example, if OpenAI Chat suggests an alternative version and the user prefers the first option, it currently disrupts the import process(only the last child/version is followed). Additionally, it never shows alternative branches or options in the UI. This feature would enhance user experience by allowing seamless switching between different chat versions.

https://betterchatgpt.canny.io/admin/board/feature-requests/p/add-branching-support-for-chats