Add SIM/LIVE switch with API keys saved to .env and OKX live executor.

Enable settings UI for mode/keys, gate strategy start when LIVE is not ready, and stop PM2 from forcing MODE=SIM.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/config.py

@@ -33,6 +33,10 @@ class Settings(BaseSettings):
     okx_ws_public: str = "wss://ws.okx.com:8443/ws/v5/public"
     okx_http_proxy: str = ""
 
+    # 币安私有交易密钥（本期仅落盘；实盘下单后续）
+    binance_api_key: str = ""
+    binance_api_secret: str = ""
+
     # 币安公共行情（SIM 只读）
     binance_fapi_base: str = "https://fapi.binance.com"
     binance_eapi_base: str = "https://eapi.binance.com"