[Enhancement]: Make Code Generation General

[wiseaidev]

Currently, BackendGPT and FrontendGPT are limited to supporting predefined programming languages such as Python, Rust, and JavaScript.

https://github.com/kevin-rs/kevin/blob/6ae9232db06362224da0e8cc0f45aab0dbcf2d26/src/agents/backend.rs#L107-L161

https://github.com/kevin-rs/kevin/blob/6ae9232db06362224da0e8cc0f45aab0dbcf2d26/src/agents/frontend.rs#L103-L160

To expand language support and enhance flexibility, we propose implementing an initial step. This involves calling the Gemini endpoint to generate a list of setup commands for the code environment. The endpoint should return a comma-separated list of commands. By looping over these commands and executing them sequentially, we can ensure a broader range of languages are supported.