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/tests/test_binance_parse.py

@@ -57,3 +57,35 @@ def test_normalize_exchange() -> None:
     assert normalize_exchange_name("BN") == "binance"
     assert normalize_exchange_name("okx") == "okx"
     assert normalize_exchange_name(None) == "okx"
+
+
+def test_binance_maps_okx_family_name() -> None:
+    """误传 OKX family 时不应按 startswith(ETH) 乱匹配，应映射到 ETHUSDT。"""
+    from app.exchange.binance.rest import BinanceRestClient
+
+    cli = BinanceRestClient.__new__(BinanceRestClient)
+    cli._exchange_info = {
+        "optionSymbols": [
+            {
+                "symbol": "ETH-260726-1860-C",
+                "underlying": "ETHUSDT",
+                "status": "TRADING",
+                "strikePrice": "1860",
+                "side": "CALL",
+                "expiryDate": 1785052800000,
+                "unit": "1",
+            },
+            {
+                "symbol": "BTC-260726-100000-C",
+                "underlying": "BTCUSDT",
+                "status": "TRADING",
+                "strikePrice": "100000",
+                "side": "CALL",
+                "expiryDate": 1785052800000,
+                "unit": "1",
+            },
+        ]
+    }
+    rows = BinanceRestClient.fetch_option_instruments(cli, "ETH-USD_UM")
+    assert len(rows) == 1
+    assert rows[0]["symbol"] == "ETH-260726-1860-C"