Mathematicaly accurate

🐛 fix(data_processing.py): fix formula for R_V_scan to include parentheses for correct order of operations 🐛 fix(output.py): add delta_z parameter to generate_headers function to correctly display the delta_z value in the output file ✨ feat(output.py): add delta_z value to output file headers if add_headers setting is enabled ✨ feat(MainWindow.py): add delta_z value to output file headers if add_headers setting is enabled ✨ feat(DiscreteDataWorker.py): add delta_z value to output file headers if add_headers setting is enabled ✨ feat(RawDataWorker.py): add delta_z value to output file headers if add_headers setting is enabled

The changes in data_processing.py fix a variable name and a formula to correctly calculate the R_max and R_V_scan values.