Complete decimal.po translation: Translate comments in code examples

- Translated comments and docstrings in all code examples while preserving code structure
- Translated threading context configuration comments
- Translated function docstrings and inline comments in utility functions (moneyfmt, pi, exp, cos, sin)
- Translated comments in memory usage and precision examples
- All untranslated entries now completed following translation guidelines

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: josix