Add taxes functionality and refactor trading logic

- Introduced Taxes class in taxes.py to calculate and apply taxes on profits in backtest results.
- Updated main.py to include tax calculations in the results processing flow.
- Refactored trade logging in TrendDetectorSimple to account for transaction fees and ensure accurate profit calculations.
- Added a utility script (apply_taxes_to_file.py) for applying taxes to existing CSV files.
- Adjusted date range and timeframe settings in main.py for broader analysis.

utils/apply_taxes_to_file.py

@@ -0,0 +1,23 @@
+import sys
+import os
+sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+from taxes import Taxes
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2:
+        print("Usage: python apply_taxes_to_file.py <input_csv> [profit_col]")
+        sys.exit(1)
+
+    input_csv = sys.argv[1]
+    profit_col = sys.argv[2] if len(sys.argv) > 2 else 'final_usd'
+
+    if not os.path.isfile(input_csv):
+        print(f"File not found: {input_csv}")
+        sys.exit(1)
+
+    base, ext = os.path.splitext(input_csv)
+    output_csv = f"{base}_taxed.csv"
+
+    taxes = Taxes()  # Default 20% tax rate
+    taxes.add_taxes_to_results_csv(input_csv, output_csv, profit_col=profit_col)
+    print(f"Taxed file saved as: {output_csv}")