Backtest a trading strategy on historical data with institutional-grade metrics.

    Args:
        symbol: Yahoo Finance symbol (AAPL, BTC-USD, THYAO.IS, ^GSPC)
        strategy: rsi | bollinger | macd | ema_cross | supertrend | donchian
                  | rsi_pullback | keltner_breakout | triple_ema
                  (rsi_pullback and triple_ema need period >= '1y' for SMA200 warmup)
        period: '1mo', '3mo', '6mo', '1y', '2y'
        initial_capital: Starting capital in USD (default $10,000)
        commission_pct: Per-trade commission % (default 0.1%)
        slippage_pct: Per-trade slippage % (default 0.05%)
        interval: '1d' (daily) or '1h' (hourly)
        include_trade_log: Include full per-trade log (default False)
        include_equity_curve: Include equity curve data points (default False)