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>

frontend/src/pages/Settings.tsx

@@ -73,6 +73,7 @@ export default function SettingsPage() {
   const [rest, setRest] = useState(300);
   const [orderInterval, setOrderInterval] = useState(1);
   const [skipWeekends, setSkipWeekends] = useState(true);
+  const [oneExpiryPerDay, setOneExpiryPerDay] = useState(true);
   const [leverage, setLeverage] = useState(3);
   const [perpMarginMode, setPerpMarginMode] = useState<"cross" | "isolated">(
     "cross",
@@ -180,6 +181,7 @@ export default function SettingsPage() {
         setRest(s.rest_seconds);
         setOrderInterval(s.live_order_interval_sec ?? 1);
         setSkipWeekends(s.skip_weekends !== false);
+        setOneExpiryPerDay(s.one_expiry_per_day !== false);
         setLeverage(s.leverage ?? 3);
         setPerpMarginMode(
           s.perp_margin_mode === "isolated" ? "isolated" : "cross",
@@ -344,6 +346,7 @@ export default function SettingsPage() {
         rest_seconds: rest,
         live_order_interval_sec: orderInterval,
         skip_weekends: skipWeekends,
+        one_expiry_per_day: oneExpiryPerDay,
         leverage,
         perp_margin_mode: perpMarginMode,
         min_option_hours: minHours,
@@ -1167,6 +1170,25 @@ export default function SettingsPage() {
                       <option value="0">关闭</option>
                     </select>
                   </div>
+                  <div className="field">
+                    <label htmlFor="oneExpDay">
+                      同到期日一天只开一次（节奏）
+                    </label>
+                    <select
+                      id="oneExpDay"
+                      className="mono"
+                      value={oneExpiryPerDay ? "1" : "0"}
+                      onChange={(e) =>
+                        setOneExpiryPerDay(e.target.value === "1")
+                      }
+                    >
+                      <option value="1">开启（推荐）</option>
+                      <option value="0">关闭</option>
+                    </select>
+                    <p className="hint" style={{ margin: "0.35rem 0 0" }}>
+                      开启后：当日已开过某到期日（如 0802）并平仓后，不能再开同到期，只能开下一到期（如 0803）。
+                    </p>
+                  </div>
                   <div className="field">
                     <label htmlFor="fee">手续费率</label>
                     <input