Replace R/rpy2 dependency with py-statmatch once ready

[MaxGhenis]

Overview

Once the py-statmatch package is ready, we should replace all R/rpy2 dependencies with the pure Python implementation.

py-statmatch Repository

https://github.com/PolicyEngine/py-statmatch

Benefits

1. No R installation required - Simplifies setup and CI/CD
2. Better cross-platform compatibility - Works on all platforms without R
3. Easier maintenance - Pure Python is easier to debug and maintain
4. Faster CI builds - No need to install R and its dependencies
5. Resolves documentation build issues - Fixes Fix JupyterBook 2.0 documentation build on GitHub Pages #92

Tasks

• Complete py-statmatch implementation with full test coverage
• Publish py-statmatch to PyPI
• Replace microimpute.utils.statmatch_hotdeck with py-statmatch
• Remove microimpute.utils.statmatch_python (temporary implementation)
• Update all imports from rpy2 to py-statmatch
• Remove rpy2 from optional dependencies in pyproject.toml
• Update documentation notebooks to use py-statmatch
• Update README and documentation

Code changes needed

1. In microimpute/models/matching.py:

   • Replace R imports with from statmatch import nnd_hotdeck

2. Remove these files:

   • microimpute/utils/statmatch_hotdeck.py
   • microimpute/utils/statmatch_python.py
   • microimpute/utils/import_helpers.py

3. Update pyproject.toml:

   • Remove matching optional dependency group
   • Add py-statmatch to main dependencies