Rewrite price lookup from WebSocket to REST API

Replace unreliable WebSocket connections with on-demand REST API calls
for spot and futures prices. Add cached trading pair list (refreshed
hourly) for symbol validation, and /refresh command for manual updates.

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

internal/data/market/main.go

@@ -4,37 +4,39 @@ import (
 	"sync"
 	"time"
 
+	"github.com/adshao/go-binance/v2"
+	"github.com/adshao/go-binance/v2/futures"
 	"github.com/rs/zerolog/log"
 )
 
 type MarketData struct {
-	mu                    sync.RWMutex
-	futureMarkPrice       map[string]float64
-	futureFundingRate     map[string]float64
-	futureNextFundingTime map[string]int64
-
-	spotPrice map[string]float64
+	// Trading pair caches
+	spotPairs           map[string]bool
+	futuresPairs        map[string]bool
+	pairCacheMutex      sync.RWMutex
+	lastPairCacheUpdate time.Time
 
 	// Alpha token cache
 	alphaTokens          map[string]AlphaTokenInfo
 	alphaCacheMutex      sync.RWMutex
 	lastAlphaCacheUpdate time.Time
+
+	// Binance REST clients
+	spotClient    *binance.Client
+	futuresClient *futures.Client
 }
 
 func NewMarketData() *MarketData {
 	log.Info().Msg("Start market service")
 	ms := &MarketData{
-		futureMarkPrice:       make(map[string]float64),
-		futureFundingRate:     make(map[string]float64),
-		futureNextFundingTime: make(map[string]int64),
-
-		spotPrice:   make(map[string]float64),
-		alphaTokens: make(map[string]AlphaTokenInfo),
+		spotPairs:     make(map[string]bool),
+		futuresPairs:  make(map[string]bool),
+		alphaTokens:   make(map[string]AlphaTokenInfo),
+		spotClient:    binance.NewClient("", ""),
+		futuresClient: futures.NewClient("", ""),
 	}
-	_ = ms.StartFutureWsMarkPrice()
-	_ = ms.StartSpotWsMarkPrice()
 
-	// Initialize Alpha token cache and refresh every hour
+	go ms.pairCacheRefreshLoop()
 	go ms.alphaCacheRefreshLoop()
 
 	return ms