fix: resolve nextra shallow clone warning and improve docs deployment

[solidsnakedev]

Problem

The documentation deployment was experiencing issues due to a shallow git clone warning from Nextra:

```
[nextra] The repository is shallow cloned, so the latest modified time will not be presented.
```

Solution

• Changed `fetch-depth` from `2` to `0` in the GitHub Actions checkout step
• This fetches the full git history, allowing Nextra to properly determine file modification times
• Resolves the shallow clone warning and ensures proper documentation generation

Changes

• Updated `.github/workflows/docs.yml` to use `fetch-depth: 0`

Testing

This should resolve the documentation deployment issues and eliminate the Nextra warning during the build process.