Configure custom domain for PyAirbyte documentation (GitHub Pages)

# Configure Custom Domain for PyAirbyte Documentation

## Summary
Set up the custom domain `py.airbyte.docs` (or `py.docs.airbyte.com`) to serve the PyAirbyte API documentation via GitHub Pages.

## Background
The PyAirbyte documentation is currently published to GitHub Pages at the default URL (https://airbytehq.github.io/PyAirbyte/). We want to configure a custom domain to make the docs accessible at a branded subdomain.

## Checklist

### 1. DNS Configuration
- [ ] Decide on the final domain name:
- Option A: `py.airbyte.docs` (requires owning `airbyte.docs` domain)
- Option B: `py.docs.airbyte.com` (subdomain of existing `airbyte.com`)
- Option C: Other format (specify: _____________)

- [ ] Add DNS records for the chosen domain:
- [ ] If using apex domain (`py.airbyte.docs`):
- Add 4 A records pointing to GitHub Pages IPs:
- `185.199.108.153`
- `185.199.109.153`
- `185.199.110.153`
- `185.199.111.153`
- [ ] If using subdomain (`py.docs.airbyte.com`):
- Add CNAME record pointing to `airbytehq.github.io`

- [ ] Verify DNS propagation (use `dig` or https://dnschecker.org)

### 2. GitHub Repository Configuration
- [ ] Navigate to PyAirbyte repository settings: https://github.com/airbytehq/PyAirbyte/settings/pages

- [ ] Under "Custom domain", enter the chosen domain name

- [ ] Wait for DNS check to complete (GitHub will verify the DNS records)

- [ ] Enable "Enforce HTTPS" once DNS check passes

### 3. Update Documentation References
- [ ] Update README.md to reference the new custom domain URL

- [ ] Update any hardcoded documentation links in the codebase

- [ ] Update the `logo_link` parameter in `docs/generate.py` if needed

### 4. Testing & Verification
- [ ] Verify the custom domain loads the documentation correctly

- [ ] Test HTTPS certificate is working

- [ ] Check that all internal links work correctly

- [ ] Verify that the old GitHub Pages URL redirects to the custom domain

- [ ] Test documentation in multiple browsers

### 5. Communication
- [ ] Announce the new documentation URL to the team

- [ ] Update any external references (blog posts, social media, etc.)

## Resources
- [GitHub Pages Custom Domain Documentation](https://docs.github.com/en/pages/configuring-a-custom-domain-for-your-github-pages-site)
- [Managing a custom domain for your GitHub Pages site](https://docs.github.com/en/pages/configuring-a-custom-domain-for-your-github-pages-site/managing-a-custom-domain-for-your-github-pages-site)
- [Verifying your custom domain for GitHub Pages](https://docs.github.com/en/pages/configuring-a-custom-domain-for-your-github-pages-site/verifying-your-custom-domain-for-github-pages)

## Notes
- The DNS changes may take up to 24-48 hours to propagate globally
- GitHub Pages will automatically provision an SSL certificate once DNS is configured
- The existing GitHub Pages URL will continue to work and redirect to the custom domain

## Related PR
- #832 - Adds Airbyte branding and styling to pdoc documentation