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

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

frontend/src/pages/Plan.tsx

@@ -298,6 +298,9 @@ export default function PlanPage() {
               {fmt(plan?.min_option_hours, 0)}h · 期权杠杆≥
               {fmt(plan?.min_option_leverage, 0)}x · {atmRule}
               {plan?.skip_weekends ? " · 周末跳过开仓" : ""}
+              {plan?.one_expiry_per_day !== false
+                ? " · 同到期日一天只开一次"
+                : ""}
             </p>
             <p>
               <span className="plan-rules-k">平仓</span>
@@ -306,6 +309,9 @@ export default function PlanPage() {
             <p>
               <span className="plan-rules-k">节奏</span>
               组间休息 {plan?.rest_seconds ?? "—"}s · 可开判定看交易账户
+              {plan?.one_expiry_per_day !== false
+                ? " · 同到期平仓后改开下一到期"
+                : ""}
             </p>
           </div>
         </details>