Fix concurrent map read/write race condition in MarketData

Add sync.RWMutex to protect future and spot price maps accessed by
WebSocket handlers (writers) and Telegram bot handlers (readers).
Also adds Alpha token support with caching.

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

internal/data/imarket.go

@@ -1,9 +1,15 @@
 package data
 
+import "me.thuanle/bbot/internal/data/market"
+
 type IMarket interface {
 	GetFuturePrice(symbol string) (float64, float64, int64, bool)
 	GetAllFundRate() (map[string]float64, map[string]int64)
 
 	GetSpotPrice(symbol string) (float64, bool)
 	GetMarginInterestRates() map[string]float64
+	
+	// Alpha token methods
+	IsAlphaToken(symbol string) bool
+	GetAlphaToken(symbol string) (market.AlphaTokenInfo, bool)
 }