Reset auto USDC cooldown in unit tests for stable assertions.

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

backend/tests/test_auto_usdc.py

@@ -34,6 +34,9 @@ def test_skip_non_okx() -> None:
 
 def test_sim_convert_to_2x_need() -> None:
     """USDC 不足 → 交易账户兑到 需×2（预留永续保证金）。"""
+    import app.strategy.auto_usdc as m
+
+    m._last_attempt_ts = 0.0
     cap = {
         "option_need_usdc": 100.0,
         "option_have_usdc": 20.0,
@@ -73,6 +76,9 @@ def test_sim_convert_to_2x_need() -> None:
 
 def test_reserve_perp_margin() -> None:
     """可兑 USDT = 交易 USDT − 永续所需。"""
+    import app.strategy.auto_usdc as m
+
+    m._last_attempt_ts = 0.0
     cap = {
         "option_need_usdc": 100.0,
         "option_have_usdc": 0.0,
@@ -93,7 +99,7 @@ def test_reserve_perp_margin() -> None:
         patch("app.strategy.auto_usdc.invalidate_live_balance_cache"),
     ):
         gs.return_value.is_sim = True
-        r = ensure_okx_trading_usdc(db=MagicMock(), cap=cap)
+        r = ensure_okx_trading_usdc(db=MagicMock(), cap=cap, force=True)
 
     assert r["acted"] is True
     assert wallets.convert.call_args.kwargs["amount"] == 50.0