Replace Bai Chat with another default provider

[FrancescoCaracciolo]

Since Bai Chat now requires login, it can't be used anymore as default provider. We should find another provider that does not need additional steps to configure. There are many providers we can use from Gpt4Free, however, I'm not able to install g4f on build. Alternatively, we can think about integrating one of those by ourselves or find another library that is easy to build