Gate one-open-per-expiry by historical expiry_ymd across days.

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

frontend/src/pages/Plan.tsx

@@ -302,7 +302,7 @@ export default function PlanPage() {
               {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"
+                ? " · 每个到期只开一次"
                 : ""}
             </p>
             <p>
@@ -313,7 +313,7 @@ export default function PlanPage() {
               <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"
+                ? " · 同到期用过后改开下一到期"
                 : ""}
             </p>
           </div>