fix: 测试网STOP_MARKET降级为STOP限价单

测试网不支持STOP_MARKET/TAKE_PROFIT_MARKET order type
检测TRADE_ENV=testnet时自动降级:
- STOP_MARKET → STOP + price + GTC
- TAKE_PROFIT_MARKET → TAKE_PROFIT + price + GTC
实盘(mainnet)不受影响

backend/live_executor.py

@@ -206,6 +206,13 @@ async def place_stop_order(session: aiohttp.ClientSession, symbol: str, side: st
         "reduceOnly": "true",
     }
 
+    # 测试网不支持STOP_MARKET/TAKE_PROFIT_MARKET，降级为STOP/TAKE_PROFIT（限价单）
+    if TRADE_ENV == "testnet" and order_type in ("STOP_MARKET", "TAKE_PROFIT_MARKET"):
+        fallback_type = "STOP" if "STOP" in order_type else "TAKE_PROFIT"
+        params["type"] = fallback_type
+        params["price"] = price_str  # 限价单需要price
+        params["timeInForce"] = "GTC"
+
     data, status = await binance_request(session, "POST", "/fapi/v1/order", params)
     if status == 200:
         logger.info(f"[{symbol}] 📌 挂{order_type} {side} @ {price_str} qty={qty_str} | orderId={data.get('orderId')}")