fix: Update ClickHouse client query method in get_position_summary

src/trading/journal.py

@@ -88,7 +88,7 @@ def get_position_summary(ticker: str) -> dict:
             GROUP BY position_id
             ORDER BY first_entry DESC
         """
-        result = client.execute(query)
+        result = client.query(query).result_rows
         columns = ['position_id', 'total_shares', 'avg_entry_price', 
                   'first_entry', 'last_entry', 'num_orders']
         return [dict(zip(columns, row)) for row in result]