Updated to latest OpenAI library

Updated the code to be compatible with the latest version of OpenAI's Python integration library, plus various bug fixes and UI improvements.

I have been unable to get PyInstaller working with PySide6 on macos, unfortunately - I don't know what the problem is, so I might just have to wait for updates on their side. That means no MacOS version for this release, I'm afraid. If anybody can get the makedistro-mac.sh script working, please let me know!