This commit replaces .netrc with uv environment variables for installing
tools from private repositories. To store credentials, I created a new
and reusable settings file for the CLI in
`$HOME/.config/crewai/settings.json`.
The issue with .netrc files is that they are applied system-wide and are
scoped by hostname, meaning we can't differentiate tool repositories
requests from regular requests to CrewAI's API.
