feat(pygal): implement box-basic

[claude]

Summary

Implements box-basic for pygal library.

Parent Issue: #204
Sub-Issue: #332
Base Branch: plot/box-basic
Attempt: 1/3

Implementation

• plots/pygal/box/box-basic/default.py

Details

• Uses pygal.Box() for box-and-whisker plot visualization
• Displays four groups with different distributions (Group A, B, C, D)
• Custom styling with project color palette (#306998, #FFD43B, #DC2626, #059669)
• White background with readable font sizes
• 4800 × 2700 px output (16:9 aspect ratio)
• Legend at bottom showing all groups

[github-actions]

✅ Plot Tests Passed

Python 3.13 (required): passed

Compatibility:

Note: Only Python 3.13 is required to pass. Python 3.12 is tested for compatibility.