fix: resolve spot and futures symbols via shared resolver

Introduce a shared token symbol resolver for spot and futures lookups while keeping alpha lookup independent, restoring prefix/remap handling and preserving spot-only fallback behavior.

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

internal/helper/binancex/resolver.go

@@ -0,0 +1,35 @@
+package binancex
+
+import (
+	"strings"
+
+	"me.thuanle/bbot/internal/data"
+)
+
+func Token2FutureSymbols(token string) []string {
+	return Token2Symbols(token)
+}
+
+func Token2SpotSymbols(token string) []string {
+	futureSymbols := Token2FutureSymbols(token)
+	spots := make([]string, 0, len(futureSymbols)+1)
+	seen := make(map[string]struct{}, len(futureSymbols)+1)
+
+	for _, futureSymbol := range futureSymbols {
+		spotSymbol := Future2SpotSymbol(futureSymbol)
+		if _, ok := seen[spotSymbol]; ok {
+			continue
+		}
+		seen[spotSymbol] = struct{}{}
+		spots = append(spots, spotSymbol)
+	}
+
+	spotOnly := strings.ToUpper(token) + "USDT"
+	if data.Market.IsSpotPair(spotOnly) {
+		if _, ok := seen[spotOnly]; !ok {
+			spots = append(spots, spotOnly)
+		}
+	}
+
+	return spots
+}