Add fixed-direction switch for perp/option open side.

When enabled, lock perp long→buy Put or short→buy Call with ITM/ATM only; off keeps ATM/ask rules.

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

backend/app/market/instruments.py

@@ -40,6 +40,7 @@ def select_option_pair(
     expiry_ymd: str | None = None,
     min_hours: float | None = None,
     now=None,
+    option_side: str | None = None,
 ) -> OptionPair | None:
     contracts = normalize_contracts(instruments)
     return _select_pair(
@@ -48,6 +49,7 @@ def select_option_pair(
         expiry_ymd=expiry_ymd,
         min_hours=min_hours,
         now=now,
+        option_side=option_side,
     )