release(pydeck-carto): Bump version to 0.2.1

[chrisgervang]

Summary

• Bump pydeck-carto version to 0.2.1
• Add changelog entry for 0.2.1 (uv migration, RTD fixes, docs updates, dep bumps)
• Update docs/conf.py release version
• Update RTD requirements

Stacked on #10197. Merge that first.

Test plan

• CI passes
• Publish to test.pypi.org
• Publish to pypi.org

🤖 Generated with Claude Code

---

Note

Low Risk
Low risk: this is a version/metadata-only release bump plus documentation/RTD requirement updates, with no runtime logic changes in the diff.

Overview
Bumps pydeck-carto from 0.2.0 to 0.2.1 across package metadata (pyproject.toml, _version.py) and Sphinx docs config (docs/conf.py).

Adds a 0.2.1 changelog entry and updates ReadTheDocs requirements to target pydeck-carto>=0.2.1.

^{Reviewed by Cursor Bugbot for commit 904c90e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coveralls]

coverage: 81.456%. remained the same — chr/pydeck-carto-0.2.1-release into master