Improve deployment robustness with consistent robocopy usage (#284)

Improve deployment robustness with consistent robocopy usage (#284)

# Improve deployment robustness with consistent robocopy usage

## Summary
Replace Move-Item with robocopy for moving current production to old directory, ensuring consistent and robust file operations throughout the deployment process.

## Details
- Created local PowerShell function `Invoke-RobocopyMirror` to eliminate code duplication
- Both "move production to old" and "copy staging to production" operations now use robocopy
- Proper exit code handling for all robocopy operations (exit codes 0-2 are success)
- Consistent logging with timestamped log files for troubleshooting
- More robust handling of large directories and locked files

## Benefits
- **Consistency**: All file operations use the same robust mechanism
- **Reliability**: robocopy handles locked files and permissions better than Move-Item
- **Maintainability**: Single function reduces code duplication
- **Troubleshooting**: Comprehensive logging for all operations
- **Performance**: More efficient for large directory operations

## Testing
- Deployment workflow logic verified
- Error handling maintains proper exit codes
- Log files generated with descriptive names

This change ensures the deployment process is more reliable and consistent across all file operations.

Co-authored-by: Pascal HAVELANGE <havelangep@hotmail.com>