Add check_symbols.py for ETH perpetuals filtering and enhance backtester with size handling

- Introduced `check_symbols.py` to load and filter ETH perpetual markets from the OKX exchange using CCXT.
- Updated the backtester to normalize signals to a 5-tuple format, incorporating size management for trades.
- Enhanced portfolio functions to support variable size and leverage adjustments based on initial capital.
- Added a new method in `CryptoQuantClient` for chunked historical data fetching to avoid API limits.
- Improved market symbol normalization in `market.py` to handle different formats.
- Updated regime strategy parameters based on recent research findings for optimal performance.

check_symbols.py

@@ -0,0 +1,28 @@
+import ccxt
+import sys
+
+def main():
+    try:
+        exchange = ccxt.okx()
+        print("Loading markets...")
+        markets = exchange.load_markets()
+        
+        # Filter for ETH perpetuals
+        eth_perps = [
+            symbol for symbol, market in markets.items() 
+            if 'ETH' in symbol and 'USDT' in symbol and market.get('swap') and market.get('linear')
+        ]
+        
+        print(f"\nFound {len(eth_perps)} ETH Linear Perps:")
+        for symbol in eth_perps:
+            market = markets[symbol]
+            print(f"  CCXT Symbol: {symbol}")
+            print(f"  Exchange ID: {market['id']}")
+            print(f"  Type: {market['type']}")
+            print("-" * 30)
+            
+    except Exception as e:
+        print(f"Error: {e}")
+
+if __name__ == "__main__":
+    main()