fix(trader): harden API calls with timeouts, strict balance parsing, error context

- binance/bybit/gate: SDK default http.DefaultClient has no timeout; use a
  dedicated 30s-timeout client so a hung connection cannot stall the loop
- bybit: stop mutating http.DefaultClient.Transport, which leaked the
  referer header into every other HTTP request in the process
- add types.ParseFloatField: empty exchange fields stay zero, but malformed
  numeric values now surface as errors instead of silently becoming zero
  balances (applied to GetBalance across 8 exchanges)
- wrap order/market-data errors in auto_trader_orders and okx cancel paths
  with symbol context; log per-order cancel failures in okx CancelAllOrders

trader/lighter/account.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"net/http"
 	"nofx/logger"
+	"nofx/trader/types"
 	"strconv"
 	"strings"
 )
@@ -113,11 +114,26 @@ func (t *LighterTraderV2) GetAccountBalance() (*AccountBalance, error) {
 	}
 
 	// Parse string values to float64
-	availableBalance, _ := strconv.ParseFloat(accountInfo.AvailableBalance, 64)
-	collateral, _ := strconv.ParseFloat(accountInfo.Collateral, 64)
-	crossAssetValue, _ := strconv.ParseFloat(accountInfo.CrossAssetValue, 64)
-	totalEquity, _ := strconv.ParseFloat(accountInfo.TotalEquity, 64)
-	unrealizedPnl, _ := strconv.ParseFloat(accountInfo.UnrealizedPnl, 64)
+	availableBalance, err := types.ParseFloatField("available_balance", accountInfo.AvailableBalance)
+	if err != nil {
+		return nil, err
+	}
+	collateral, err := types.ParseFloatField("collateral", accountInfo.Collateral)
+	if err != nil {
+		return nil, err
+	}
+	crossAssetValue, err := types.ParseFloatField("cross_asset_value", accountInfo.CrossAssetValue)
+	if err != nil {
+		return nil, err
+	}
+	totalEquity, err := types.ParseFloatField("total_equity", accountInfo.TotalEquity)
+	if err != nil {
+		return nil, err
+	}
+	unrealizedPnl, err := types.ParseFloatField("unrealized_pnl", accountInfo.UnrealizedPnl)
+	if err != nil {
+		return nil, err
+	}
 
 	// Use collateral as total equity if total_equity is 0
 	if totalEquity == 0 {