feat(backtest): add ResultsAnalyzer for metrics and trade analysis - Issue #43 (42 tests)
Implements comprehensive post-backtest analysis:
- TradeAnalysis, TradePattern, PerformanceBreakdown dataclasses
- RiskMetrics: Sharpe, Sortino, Calmar, VaR, CVaR, Ulcer index
- TradeStatistics: Win rate, profit factor, streaks, averages
- BenchmarkComparison: Alpha, beta, correlation, capture ratios
- DrawdownAnalysis: Underwater periods, recovery tracking
- AnalysisResult: Complete analysis output
- Monthly and yearly performance breakdown
- Best/worst trade identification
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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