Add Binance SIM market adapter and exchange switch in settings.

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

frontend/src/pages/Settings.tsx

@@ -35,6 +35,7 @@ export default function SettingsPage() {
   const [perpQty, setPerpQty] = useState(1);
   const [optQty, setOptQty] = useState(2);
   const [initialEquity, setInitialEquity] = useState(10000);
+  const [exchange, setExchange] = useState<"okx" | "binance">("okx");
   const [stratOk, setStratOk] = useState("");
 
   useEffect(() => {
@@ -53,6 +54,7 @@ export default function SettingsPage() {
         setPerpQty(s.perp_qty_eth ?? 1);
         setOptQty(s.option_qty_eth ?? 2);
         setInitialEquity(s.initial_equity ?? 10000);
+        setExchange(s.exchange === "binance" ? "binance" : "okx");
       })
       .catch(() => undefined);
   }, []);
@@ -109,10 +111,11 @@ export default function SettingsPage() {
           perp_qty_eth: perpQty,
           option_qty_eth: optQty,
           initial_equity: initialEquity,
+          exchange,
         }),
       });
       setStratOk(
-        "策略参数已保存（模拟资金仅在数值变更且无持仓时重置账本）",
+        "策略参数已保存（切换交易所/改模拟资金需无持仓；切换后会重连行情）",
       );
     } catch (ex) {
       setErr(ex instanceof Error ? ex.message : String(ex));
@@ -142,11 +145,34 @@ export default function SettingsPage() {
       {tab === "strategy" ? (
         <div className="card settings-card">
           <p className="settings-lead">
-            无开仓时间窗；可选周六日跳过开仓；期权按剩余时长选到期 → 平值 → 校验杠杆；出场可选固定金额或权利金倍数。
+            无开仓时间窗；可切换 OKX / 币安行情（SIM 本地撮合）；周六日可跳过开仓；出场按净盈利或到期全平。
           </p>
           {stratOk ? <div className="settings-ok">{stratOk}</div> : null}
           {err && tab === "strategy" ? <div className="err">{err}</div> : null}
           <form onSubmit={onSaveStrategy}>
+            <section className="settings-section">
+              <h3>交易所</h3>
+              <div className="settings-fields">
+                <div className="field">
+                  <label htmlFor="exch">行情交易所（SIM 只读）</label>
+                  <select
+                    id="exch"
+                    className="mono"
+                    value={exchange}
+                    onChange={(e) =>
+                      setExchange(e.target.value === "binance" ? "binance" : "okx")
+                    }
+                  >
+                    <option value="okx">OKX（USDC 期权族）</option>
+                    <option value="binance">币安（USDT 永续 + 欧洲期权）</option>
+                  </select>
+                  <p className="settings-hint">
+                    有持仓时不可切换。切换后自动套用该所合约并重连公共行情。
+                  </p>
+                </div>
+              </div>
+            </section>
+
             <section className="settings-section">
               <h3>资金</h3>
               <div className="settings-fields">