Add comprehensive Python package installation guide for Apptainer containers

[Copilot]

This PR adds detailed documentation for adding Python packages to the Roberts Lab Apptainer container used on Klone. The new section addresses a common question from lab members about how to incorporate Python packages into their shared bioinformatics container.

What's Added

The documentation includes four different methods for installing Python packages:

1. System Python packages (via apt) - For basic packages available in Ubuntu repositories
2. pip packages - With proper caching and optimization flags
3. Conda/Mamba environments - Leveraging the existing Miniforge installation
4. GitHub and custom sources - For packages not in standard repositories

Key Features

• Best practices section covering version pinning, cache optimization, package grouping, and choosing the right installation method
• Complete example showing how to add common data science packages (numpy, pandas, matplotlib, seaborn, scikit-learn, biopython, jupyter, etc.)
• Clear code examples with proper bash syntax for the Apptainer definition file
• Integration with existing workflow that references the actual container definition file location

The documentation emphasizes that software cannot be installed after container build, reinforcing the importance of updating the definition file and rebuilding the container.

This provides lab members with actionable guidance for extending the shared bioinformatics container with their specific Python package requirements while maintaining best practices for container optimization and reproducibility.

Fixes #2277.

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