refactor: standardize market filenames by data dimension

Split market pair logic into spot and futures files and rename price files to plural data-dimension names without changing behavior.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/data/market/spot_prices.go

@@ -0,0 +1,42 @@
+package market
+
+import (
+	"context"
+	"strconv"
+	"time"
+
+	"github.com/rs/zerolog/log"
+)
+
+func (ms *MarketData) GetSpotPrice(symbol string) (float64, bool) {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	prices, err := ms.spotClient.NewListPricesService().Symbol(symbol).Do(ctx)
+	if err != nil {
+		log.Error().Err(err).Str("symbol", symbol).Msg("Failed to fetch spot price")
+		return ms.getAlphaPrice(symbol)
+	}
+
+	if len(prices) == 0 {
+		return ms.getAlphaPrice(symbol)
+	}
+
+	price, err := strconv.ParseFloat(prices[0].Price, 64)
+	if err != nil || price == 0 {
+		return ms.getAlphaPrice(symbol)
+	}
+
+	return price, true
+}
+
+func (ms *MarketData) getAlphaPrice(symbol string) (float64, bool) {
+	if ms.IsAlphaToken(symbol) {
+		if alphaToken, exists := ms.GetAlphaToken(symbol); exists {
+			if price := alphaToken.GetPrice(); price > 0 {
+				return price, true
+			}
+		}
+	}
+	return 0, false
+}