fix: remove recvWindow from exchange_info wrapper

Binance exchangeInfo endpoint does not accept recvWindow, causing
RuntimeError when calling opportunity scan or any command that hits
exchange_info().

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/coinhunter/binance/spot_client.py

@@ -44,7 +44,7 @@ class SpotBinanceClient:
         return self._call("account info", self._client.account, recvWindow=self.recv_window)  # type: ignore[no-any-return]
 
     def exchange_info(self, symbol: str | None = None) -> dict[str, Any]:
-        kwargs: dict[str, Any] = {"recvWindow": self.recv_window}
+        kwargs: dict[str, Any] = {}
         if symbol:
             kwargs["symbol"] = symbol
         return self._call("exchange info", self._client.exchange_info, **kwargs)  # type: ignore[no-any-return]