fix: critical production issues — WebSocket reconnect, ghost positions, ONNX NaN

- fix(data_stream): add reconnect loop to MultiSymbolStream matching UserDataStream pattern
  Prevents bot-wide crash on WebSocket disconnect (#3 Critical)

- fix(data_stream): increase buffer_size 200→300 and preload 200→300
  Ensures z-score window (288) has sufficient data (#5 Important)

- fix(bot): sync risk manager when Binance has no position but local state does
  Prevents ghost entries in open_positions blocking future trades (#1 Critical)

- fix(ml_filter): add np.nan_to_num for ONNX input to handle NaN features
  Prevents all signals being blocked during initial ~2h warmup (#2 Critical)

- fix(bot): replace _close_handled_by_sync with current_trade_side==None guard
  Eliminates race window in SYNC PnL double recording (#4 Important)

- feat(bot): add _ensure_sl_tp_orders in _recover_position
  Detects and re-places missing SL/TP orders on bot restart (#6 Important)

- feat(exchange): add get_open_orders method for SL/TP verification

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

src/exchange.py

@@ -145,6 +145,14 @@ class BinanceFuturesClient:
                 return p
         return None
 
+    async def get_open_orders(self) -> list[dict]:
+        """현재 심볼의 오픈 주문 목록을 조회한다."""
+        loop = asyncio.get_running_loop()
+        return await loop.run_in_executor(
+            None,
+            lambda: self.client.futures_get_open_orders(symbol=self.symbol),
+        )
+
     async def cancel_all_orders(self):
         """오픈 주문을 모두 취소한다."""
         loop = asyncio.get_running_loop()