Use trading account and USDC/USDT market price for sim convert.

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

lib/common/static/options_settings.js

@@ -101,14 +101,14 @@
   async function resolveSwapMaxAmount(dir) {
     const bal = await loadBalances(true, "main");
     const ccy = dir === "usdc_to_usdt" ? "USDC" : "USDT";
-    // 币种兑换走资金账户现货;统一账户下 USDT 有时在交易户,市价单仍可能成交
-    let amount = pickBalance(bal, "funding", ccy);
-    let source = "funding";
-    if (!amount && ccy === "USDT") {
-      const tradingAmt = pickBalance(bal, "trading", ccy);
-      if (tradingAmt) {
-        amount = tradingAmt;
-        source = "trading";
+    // 现货 USDC-USDT 走交易账户(cash); 交易户不足时再看资金户
+    let amount = pickBalance(bal, "trading", ccy);
+    let source = "trading";
+    if (!amount) {
+      const fundingAmt = pickBalance(bal, "funding", ccy);
+      if (fundingAmt) {
+        amount = fundingAmt;
+        source = "funding";
       }
     }
     return { amount, bal, ccy, source };