Update upload.py - Move code to functions and update operations

[rowingdude]

• Migrate to Python 3.6+ syntax
• Add type hinting
• Use pathlib for file operations
• Implement argparse for CLI
• Refactor into smaller functions
• Improve input validation and error handling

[mcspr]

Ok, but how does this work? Changing arguments from positional to --... would break when attempting an upload?