feat: add pending orders (SL/TP) display on chart

- Add GetOpenOrders method to Trader interface
- Implement for Binance (legacy + Algo), Bybit, Hyperliquid
- Add stub implementations for OKX, Bitget, Aster, Lighter
- Add /api/open-orders endpoint
- Display price lines for SL (red) and TP (green) orders
- Refresh open orders every 60 seconds (separate from 5s kline refresh)

trader/auto_trader.go

@@ -2218,3 +2218,8 @@ func getSideFromAction(action string) string {
 	}
 }
 
+// GetOpenOrders returns open orders (pending SL/TP) from exchange
+func (at *AutoTrader) GetOpenOrders(symbol string) ([]OpenOrder, error) {
+	return at.trader.GetOpenOrders(symbol)
+}
+