Route manual USDT/USDC convert through trading account (not funding).

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

backend/app/api/funds.py

@@ -167,11 +167,15 @@ async def funds_summary(_user: Annotated[str, Depends(require_user)]) -> dict[st
 async def funds_convert(
     body: ConvertBody, _user: Annotated[str, Depends(require_user)]
 ) -> dict[str, Any]:
+    """USDT↔USDC 市价兑换：一律在交易账户（对齐 OKX 现货 cash；SIM 同口径）。"""
     s = get_settings()
     rate = usdc_usdt_mid_rate()
     if s.is_sim:
         r = SimFundsWallets(get_db()).convert(
-            direction=body.direction, amount=float(body.amount), rate=rate
+            direction=body.direction,
+            amount=float(body.amount),
+            rate=rate,
+            account="trading",
         )
         if not r.get("ok"):
             raise HTTPException(status_code=400, detail=r.get("detail") or "兑换失败")
@@ -186,6 +190,12 @@ async def funds_convert(
         )
     finally:
         client.close()
+    try:
+        from ..strategy.open_capacity import invalidate_live_balance_cache
+
+        invalidate_live_balance_cache()
+    except Exception:
+        pass
     if not r.get("ok"):
         raise HTTPException(status_code=400, detail=r.get("detail") or "兑换失败")
     return r

docs/更新说明.md

@@ -5,6 +5,15 @@
 
 ---
 
+## 2026-07-30 — 手动兑换改走交易账户
+
+### 变更
+
+1. `/api/funds/convert`（SIM）改为 `account=trading`；LIVE 本就现货交易账户，兑换后清余额缓存。  
+2. 设置页文案改为「交易账户」兑换。
+
+---
+
 ## 2026-07-30 — 持仓锁定出场目标 / 暂停以损定仓重算
 
 ### 变更

frontend/src/pages/Settings.tsx

@@ -1474,8 +1474,8 @@ export default function SettingsPage() {
             onToggle={() => setFundsRulesOpen((v) => !v)}
           >
             <p>
-              币种兑换：对齐 OKX 现货市价 USDC-USDT，手动兑换在<strong>资金账户</strong>
-              内完成。参考价{" "}
+              币种兑换：对齐 OKX 现货市价 USDC-USDT，在<strong>交易账户</strong>
+              内完成（不走资金账户）。参考价{" "}
               {usdcRate != null ? `1 USDC ≈ ${usdcRate.toFixed(4)} USDT` : "—"}。
             </p>
             <p>
@@ -1489,7 +1489,7 @@ export default function SettingsPage() {
           </RulesFold>
 
           <section className="settings-section">
-            <h3>币种兑换（USDT ↔ USDC）</h3>
+            <h3>币种兑换（交易账户 · USDT ↔ USDC）</h3>
             <div className="settings-fields">
               <div className="field">
                 <label htmlFor="convertDir">方向</label>