fix: use taker fees (BG 0.06%, HL 0.045%) + threshold 0.25%

All IOC market orders incur taker fees, not maker fees. Previous
makerFees (BG 0.02%, HL 0.015%) caused 0.10% threshold trades to
actually lose 0.11% per round trip.

Changes:
- scanner.go: makerFees → takerFees (BG 0.060, HL 0.045)
- dashboard.go: makerFees → takerFees
- types.go: makerFees → takerFees
- trader.go: makerFees → takerFees
- config.json: trade_threshold 0.1 → 0.25

scanner.go

@@ -10,10 +10,10 @@ const (
 	ExBitget      = "Bitget"
 )
 
-// Maker fee rates (%) — for limit orders on trading exchanges
-var makerFees = map[string]float64{
-	ExHyperLiquid: 0.015,
-	ExBitget:      0.020, // standard maker
+// Taker fee rates (%) — for IOC market orders on trading exchanges
+var takerFees = map[string]float64{
+	ExHyperLiquid: 0.045,
+	ExBitget:      0.060,
 }
 
 // TickerCoins defines all coins we monitor.
@@ -59,9 +59,9 @@ func ScanBGHL(store *PriceStore) []*ArbOpportunity {
 		}
 
 		// BG->HL: buy cheap at Bitget, sell expensive at HyperLiquid
-		profitBG := netProfit(bgP, hlP, makerFees[ExBitget], makerFees[ExHyperLiquid])
+		profitBG := netProfit(bgP, hlP, takerFees[ExBitget], takerFees[ExHyperLiquid])
 		// HL->BG: buy cheap at HyperLiquid, sell expensive at Bitget
-		profitHL := netProfit(hlP, bgP, makerFees[ExHyperLiquid], makerFees[ExBitget])
+		profitHL := netProfit(hlP, bgP, takerFees[ExHyperLiquid], takerFees[ExBitget])
 
 		grossBG := (hlP - bgP) / bgP * 100
 		grossHL := (bgP - hlP) / hlP * 100