feat: 15 funciones finance — indicadores, riesgo e IO de mercado

11 funciones puras con implementación real:
SMA, EMA, RSI, BollingerBands, VWAP, LogReturn, AnnualizedVolatility,
SharpeRatio, MaxDrawdown, NormalizeOHLCV, TickToOHLCV

4 funciones impuras (stubs):
FetchOHLCV, StreamTicks, WriteOHLCVToParquet, LoadOHLCVFromDuckDB

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

functions/finance/normalize_ohlcv.go

@@ -0,0 +1,17 @@
+package finance
+
+// NormalizeOHLCV ajusta slices de precios OHLCV multiplicando por un factor.
+func NormalizeOHLCV(open, high, low, close []float64, factor float64) ([]float64, []float64, []float64, []float64) {
+	n := len(open)
+	nOpen := make([]float64, n)
+	nHigh := make([]float64, n)
+	nLow := make([]float64, n)
+	nClose := make([]float64, n)
+	for i := 0; i < n; i++ {
+		nOpen[i] = open[i] * factor
+		nHigh[i] = high[i] * factor
+		nLow[i] = low[i] * factor
+		nClose[i] = close[i] * factor
+	}
+	return nOpen, nHigh, nLow, nClose
+}