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/exchange/types.py

@@ -88,7 +88,26 @@ def _open_bias(
     call: Quote | None,
     put: Quote | None,
 ) -> str:
-    """与开仓 decide 一致：先按 ATM 相对现价，贴平时再卖一比价。"""
+    """与开仓 decide 一致；固定方向开启时显示 fixed_*。"""
+    try:
+        from ..config import get_settings
+        from ..models.db import get_db
+
+        s = get_settings()
+        db = get_db()
+        raw = db.get_setting(
+            "fixed_direction_enabled", str(s.fixed_direction_enabled)
+        )
+        on = str(raw or "").strip().lower() in ("1", "true", "yes", "on")
+        if on:
+            side = str(
+                db.get_setting("fixed_perp_side", s.fixed_perp_side)
+                or s.fixed_perp_side
+                or "long"
+            ).strip().lower()
+            return "fixed_long_put" if side == "long" else "fixed_short_call"
+    except Exception:
+        pass
     mark = None
     if index_px is not None and index_px > 0:
         mark = float(index_px)