v2.8.0 - Comprehensive Distribution Testing Framework & Bug Fixes

174 standardized test cases across all distributions
• Organized by statistical families (location-scale, gamma family, etc.)
• Comprehensive parameter validation and statistical property verification
• Robust error handling and edge case testing
• 100% test success rate providing rigorous mathematical validation

🐛 Critical Bug Fixes:
• Fixed Pareto distribution boundary condition bug - proper PDF calculation at x=x_m
• Ensures mathematical correctness for power law distributions
• Added Rayleigh distribution to main distributions header for completeness