Fix Binance boot using OKX symbols after restart.

Startup ignored DB exchange choice and kept OKX ATM ids under a Binance health label, so option bid/ask stayed empty.

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

backend/app/exchange/binance/rest.py

@@ -55,19 +55,25 @@ class BinanceRestClient:
         return self._exchange_info
 
     def fetch_option_instruments(self, underlying: str) -> list[dict[str, Any]]:
-        """underlying 如 ETH / ETHUSDT。"""
+        """underlying 如 ETH / ETHUSDT。误传 OKX family（ETH-USD_UM）时映射到 ETHUSDT。"""
         info = self.fetch_option_exchange_info()
         rows = info.get("optionSymbols") or info.get("symbols") or []
         want = (underlying or "ETHUSDT").strip().upper()
-        eth_mode = want in ("ETH", "ETHUSDT") or want.startswith("ETH")
+        # 兼容误用 OKX 期权族名
+        if "USD_UM" in want or want in ("ETH-USD", "ETH-USDT", "ETHUSD"):
+            want = "ETHUSDT"
+        eth_mode = want in ("ETH", "ETHUSDT") or (
+            want.startswith("ETH") and "-" not in want
+        )
         out: list[dict[str, Any]] = []
         for row in rows:
             if not isinstance(row, dict):
                 continue
             u = str(row.get("underlying") or row.get("underlyingAsset") or "").upper()
             sym = str(row.get("symbol") or "").upper()
+            # 只收币安格式 ETH-YYMMDD-STRIKE-C/P，避免脏符号进缓存
             if eth_mode:
-                if sym.startswith("ETH-") or u.startswith("ETH"):
+                if sym.startswith("ETH-") and u.startswith("ETH"):
                     out.append(row)
                 continue
             base = want.replace("USDT", "") if want.endswith("USDT") else want