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/tick_to_ohlcv.go

@@ -0,0 +1,53 @@
+package finance
+
+// TickToOHLCV agrega datos de ticks en velas OHLCV segun un intervalo en segundos.
+// prices, volumes y timestamps deben tener la misma longitud.
+// timestamps son unix seconds. intervalSecs define el ancho de cada vela.
+// Retorna slices de open, high, low, close, volume para cada vela generada.
+func TickToOHLCV(prices, volumes []float64, timestamps []int64, intervalSecs int64) (open, high, low, close, vol []float64) {
+	n := len(prices)
+	if n == 0 || intervalSecs <= 0 {
+		return
+	}
+	bucketStart := timestamps[0] - (timestamps[0] % intervalSecs)
+	o := prices[0]
+	h := prices[0]
+	l := prices[0]
+	c := prices[0]
+	v := volumes[0]
+
+	for i := 1; i < n; i++ {
+		currentBucket := timestamps[i] - (timestamps[i] % intervalSecs)
+		if currentBucket != bucketStart {
+			// Cerrar la vela anterior
+			open = append(open, o)
+			high = append(high, h)
+			low = append(low, l)
+			close = append(close, c)
+			vol = append(vol, v)
+			// Nueva vela
+			bucketStart = currentBucket
+			o = prices[i]
+			h = prices[i]
+			l = prices[i]
+			c = prices[i]
+			v = volumes[i]
+		} else {
+			if prices[i] > h {
+				h = prices[i]
+			}
+			if prices[i] < l {
+				l = prices[i]
+			}
+			c = prices[i]
+			v += volumes[i]
+		}
+	}
+	// Cerrar ultima vela
+	open = append(open, o)
+	high = append(high, h)
+	low = append(low, l)
+	close = append(close, c)
+	vol = append(vol, v)
+	return
+}