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/stream_ticks.md

@@ -0,0 +1,31 @@
+---
+name: stream_ticks
+kind: function
+lang: go
+domain: finance
+version: "1.0.0"
+purity: impure
+signature: "func StreamTicks(symbol string) (<-chan [2]float64, error)"
+description: "Abre un stream de ticks en tiempo real para un simbolo via websocket."
+tags: [finance, io, stream, realtime]
+uses_functions: []
+uses_types: [tick_go_finance]
+returns: [tick_go_finance]
+returns_optional: false
+error_type: "error_go_core"
+imports: [fmt]
+tested: false
+tests: []
+test_file_path: ""
+file_path: "functions/finance/stream_ticks.go"
+---
+
+# stream_ticks
+
+Stub para abrir un stream de ticks en tiempo real. Pendiente de implementacion.
+
+## Ejemplo
+
+```go
+ch, err := finance.StreamTicks("ETH/USDT")
+```