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

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

backend/tests/test_exit_lock.py

@@ -0,0 +1,42 @@
+"""持仓锁定出场目标。"""
+
+from __future__ import annotations
+
+from app.strategy.exits import check_exits, resolve_exit_target
+
+
+def test_locked_target_ignores_setting_drift() -> None:
+    d = check_exits(
+        net_pnl=20.0,
+        exit_mode="fixed_usdt",
+        net_profit_target=50.0,  # 设置已被改大
+        premium_exit_multiple=1.0,
+        initial_premium=10.0,
+        locked_exit_target=15.0,  # 开仓锁定
+    )
+    assert d.should_close is True
+    assert d.target == 15.0
+
+
+def test_locked_target_not_yet() -> None:
+    d = check_exits(
+        net_pnl=10.0,
+        exit_mode="fixed_usdt",
+        net_profit_target=5.0,
+        premium_exit_multiple=1.0,
+        initial_premium=10.0,
+        locked_exit_target=15.0,
+    )
+    assert d.should_close is False
+    assert d.target == 15.0
+
+
+def test_resolve_premium_still_works_without_lock() -> None:
+    t, mode = resolve_exit_target(
+        exit_mode="premium_multiple",
+        net_profit_target=15.0,
+        premium_exit_multiple=2.0,
+        initial_premium=10.0,
+    )
+    assert t == 20.0
+    assert mode == "premium_multiple"