Remove deprecated app_new.py and consolidate main application logic into main.py

- Deleted `app_new.py`, which was previously the main entry point for the dashboard application, to streamline the codebase.
- Consolidated the application initialization and callback registration logic into `main.py`, enhancing modularity and maintainability.
- Updated the logging and error handling practices in `main.py` to ensure consistent application behavior and improved debugging capabilities.

These changes simplify the application structure, aligning with project standards for modularity and maintainability.

database/repositories/market_data_repository.py

@@ -2,6 +2,7 @@
 
 from datetime import datetime
 from typing import List, Optional, Dict, Any
+import pandas as pd
 
 from sqlalchemy import desc
 from sqlalchemy.dialects.postgresql import insert
@@ -136,4 +137,62 @@ class MarketDataRepository(BaseRepository):
                 
         except Exception as e:
             self.log_error(f"Error retrieving latest candle for {symbol} {timeframe}: {e}")
-            raise DatabaseOperationError(f"Failed to retrieve latest candle: {e}") 
+            raise DatabaseOperationError(f"Failed to retrieve latest candle: {e}")
+
+    def get_candles_df(self, 
+                       symbol: str, 
+                       timeframe: str, 
+                       start_time: datetime, 
+                       end_time: datetime,
+                       exchange: str = "okx") -> pd.DataFrame:
+        """
+        Retrieve candles from the database as a Pandas DataFrame using the ORM.
+        
+        Args:
+            symbol: The trading symbol (e.g., 'BTC-USDT').
+            timeframe: The timeframe of the candles (e.g., '1h').
+            start_time: The start datetime for the data.
+            end_time: The end datetime for the data.
+            exchange: The exchange name (default: 'okx').
+            
+        Returns:
+            A Pandas DataFrame containing the fetched candles, or an empty DataFrame if no data is found.
+        """
+        try:
+            with self.get_session() as session:
+                query = (
+                    session.query(MarketData)
+                    .filter(
+                        MarketData.exchange == exchange,
+                        MarketData.symbol == symbol,
+                        MarketData.timeframe == timeframe,
+                        MarketData.timestamp >= start_time,
+                        MarketData.timestamp <= end_time
+                    )
+                    .order_by(MarketData.timestamp.asc())
+                )
+                
+                # Convert query results to a list of dictionaries, then to DataFrame
+                results = [
+                    {
+                        "timestamp": r.timestamp,
+                        "open": float(r.open),
+                        "high": float(r.high),
+                        "low": float(r.low),
+                        "close": float(r.close),
+                        "volume": float(r.volume),
+                        "trades_count": int(r.trades_count) if r.trades_count else 0
+                    } for r in query.all()
+                ]
+                
+                df = pd.DataFrame(results)
+                if not df.empty:
+                    df['timestamp'] = pd.to_datetime(df['timestamp'])
+                    df = df.set_index('timestamp')
+                
+                self.log_debug(f"Retrieved {len(df)} candles as DataFrame for {symbol} {timeframe}")
+                return df
+                
+        except Exception as e:
+            self.log_error(f"Error retrieving candles as DataFrame: {e}")
+            raise DatabaseOperationError(f"Failed to retrieve candles as DataFrame: {e}")