leptonai install makes Docker image huge - use the slim package

## What happened

Installing leptonai via poetry made my Docker image 10x bigger because of all the extra dependencies like CUDA. Deployment takes forever now. Is there a lighter install option?

## The fix that worked

Yes, this was fixed in 0.18.0. The package was split in two: plain leptonai has no CUDA dependencies and stays small, while leptonai[runtime] has the full set. If you only need the client and deployment tooling in your image, install leptonai without the runtime extra and your image size drops back down.