Add OKX trading-account USDC auto-swap and lock exit target while in position.

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

backend/app/strategy/open_capacity.py

@@ -20,6 +20,12 @@ _LIVE_BAL_TTL_SEC = 8.0
 _notified_while_short: bool = False
 
 
+def invalidate_live_balance_cache() -> None:
+    """兑换/划转后强制下次重拉交易账户余额。"""
+    _live_bal_cache["ts"] = 0.0
+    _live_bal_cache["data"] = None
+
+
 def _f(v: Any) -> float | None:
     try:
         if v is None or v == "":
@@ -211,7 +217,7 @@ def maybe_notify_funds_short(cap: dict[str, Any] | None = None) -> None:
                     f"**永续**: {cap.get('perp_label')}",
                     f"**期权**: {cap.get('option_label')}",
                     *[f"**详情**: {p}" for p in parts],
-                    "请从资金账户划转到交易账户后重试。",
+                    "OKX 开仓前会尝试交易账户市价兑 USDC；仍不足请检查交易账户余额。",
                 ],
             )
         )