fix: address critical code review issues (PnL double recording, sync HTTP, race conditions)

- fix(bot): prevent PnL double recording in _close_and_reenter using asyncio.Event
- fix(bot): prevent SYNC detection PnL duplication with _close_handled_by_sync flag
- fix(notifier): move sync HTTP call to background thread via run_in_executor
- fix(risk_manager): make is_trading_allowed async with lock for thread safety
- fix(exchange): cache exchange info at class level (1 API call for all symbols)
- fix(exchange): use `is not None` instead of truthy check for price/stop_price
- refactor(backtester): extract _calc_trade_stats to eliminate code duplication
- fix(ml_features): apply rolling z-score to OI/funding rate in serving (train-serve skew)
- fix(bot): use config.correlation_symbols instead of hardcoded BTCUSDT/ETHUSDT
- fix(bot): expand OI/funding history deque to 96 for z-score window
- cleanup(config): remove unused stop_loss_pct, take_profit_pct, trailing_stop_pct fields

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/risk_manager.py

@@ -12,17 +12,18 @@ class RiskManager:
         self.open_positions: dict[str, str] = {}  # {symbol: side}
         self._lock = asyncio.Lock()
 
-    def is_trading_allowed(self) -> bool:
+    async def is_trading_allowed(self) -> bool:
         """일일 최대 손실 초과 시 거래 중단"""
-        if self.initial_balance <= 0:
+        async with self._lock:
+            if self.initial_balance <= 0:
+                return True
+            loss_pct = abs(self.daily_pnl) / self.initial_balance
+            if self.daily_pnl < 0 and loss_pct >= self.max_daily_loss_pct:
+                logger.warning(
+                    f"일일 손실 한도 초과: {loss_pct:.2%} >= {self.max_daily_loss_pct:.2%}"
+                )
+                return False
             return True
-        loss_pct = abs(self.daily_pnl) / self.initial_balance
-        if self.daily_pnl < 0 and loss_pct >= self.max_daily_loss_pct:
-            logger.warning(
-                f"일일 손실 한도 초과: {loss_pct:.2%} >= {self.max_daily_loss_pct:.2%}"
-            )
-            return False
-        return True
 
     async def can_open_new_position(self, symbol: str, side: str) -> bool:
         """포지션 오픈 가능 여부 (전체 한도 + 중복 진입 + 동일 방향 제한)"""