Add one-expiry-per-day open rhythm gate (default on).

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

backend/app/api/sim.py

@@ -59,7 +59,8 @@ async def sim_open_group(
     if ex.has_open_position():
         raise HTTPException(status_code=409, detail="有未平仓，禁止开下一组")
     s = get_settings()
-    skip_weekends = Ledger().get_setting_bool("skip_weekends", s.skip_weekends)
+    ledger = Ledger()
+    skip_weekends = ledger.get_setting_bool("skip_weekends", s.skip_weekends)
     if not can_open_new(skip_weekends=skip_weekends):
         raise HTTPException(
             status_code=409,
@@ -72,6 +73,22 @@ async def sim_open_group(
             status_code=409,
             detail="无合格期权：请检查剩余时长、ATM开仓偏差(若已开启)与杠杆(现价/卖一)",
         )
+    one_expiry = ledger.get_setting_bool("one_expiry_per_day", s.one_expiry_per_day)
+    if one_expiry:
+        from ..strategy.clock import (
+            expiry_blocked_by_one_per_day,
+            used_expiry_ymds_for_day,
+        )
+
+        used = used_expiry_ymds_for_day(get_db())
+        if expiry_blocked_by_one_per_day(pick.pair.expiry_ymd, used, enabled=True):
+            raise HTTPException(
+                status_code=409,
+                detail=(
+                    f"同到期日一天只开一次：今日已用过 {pick.pair.expiry_ymd}，"
+                    "请等下一到期日"
+                ),
+            )
 
     force = (body.force_option_side if body else None) or None
     if force in ("call", "put"):