Enhance FactorReport with HTML output and additional metrics

[novis10813]

Summary

Extend FactorReport.generate() to produce rich HTML reports with interactive charts and additional analysis metrics (IC decay, factor correlation, regime analysis).

Background

Current FactorReport.generate() produces text-based reports. HTML reports with interactive visualizations would be more useful for sharing and analysis.

Goals

• Generate HTML reports with embedded charts
• Include all analysis results (IC, IC decay, quantile returns, etc.)
• Support interactive visualizations (using plotly or similar)

Proposed Tasks

• Extend FactorReport.generate() to support format="html" option
• Create HTML template with:
  • Summary statistics table
  • Interactive IC time series chart
  • IC decay curve (after Issue Add multi-horizon IC decay and flexible targets to factor analysis #4)
  • Quantile returns visualization
  • Factor correlation heatmap (after correlation issue)
  • Regime analysis charts (after regime issue)
• Add FactorReport.generate_html(output_path: str) method
• Use plotly or similar for interactive charts (or static matplotlib with better styling)
• Add unit tests for HTML generation
• Update documentation with examples

Notes

• Should integrate with existing FactorAnalysisResult data
• Consider making HTML optional (keep text format as default)
• Charts should be self-contained (embedded, not external files)
• Consider using jinja2 for templating