Add Binance live trading, anti-stuck open/close recovery, and configurable rate limits.

OKX/Binance LIVE share half_open and option_closed_perp_pending repair paths; private REST throttles default to 1s and are tunable in settings.

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

backend/app/env_store.py

@@ -59,7 +59,7 @@ def live_ready(*, exchange: str | None = None) -> tuple[bool, str]:
     if ex == "binance":
         if not binance_keys_configured(st):
             return False, "币安 API Key/Secret 未配置"
-        return False, "币安实盘下单尚未接入，请切回 OKX 或使用 SIM"
+        return True, "ok"
     if ex == "okx":
         if not okx_keys_configured(st):
             return False, "OKX API Key/Secret/Passphrase 未配置"