feat(execution): AccountOrderWorker로 매수·매도 주문 직렬화

전략별 tick/scan 매도 락 대신 계좌 단일 PriorityQueue로 place를 B-full 직렬화한다.
틱매도 only_code 필터와 inflight 중복 enqueue 방지로 REST 폭주를 줄인다.

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

kis_trader/strategies/momentum.py

@@ -272,7 +272,7 @@ class MomentumStrategy(BaseStrategy):
             "entry_features": {},
         }
 
-    def check_sell_signals(self) -> List[Dict]:
+    def check_sell_signals(self, only_code: Optional[str] = None) -> List[Dict]:
         if not self.holdings:
             return []
 
@@ -284,9 +284,15 @@ class MomentumStrategy(BaseStrategy):
             now,
             default_hm="15:20",
         )
-        params_base = dict(self._engine_params or me.get_momentum_defaults_from_db())
+        cached = getattr(self, "_engine_params", None)
+        if cached:
+            params_base = dict(cached)
+        else:
+            params_base = dict(me.get_momentum_defaults_from_db())
 
         for code, holding in list(self.holdings.items()):
+            if only_code and code != only_code:
+                continue
             try:
                 name = holding.get("name", code)
                 buy_price = float(holding.get("buy_price", 0))