Update header line in Python files

[UltralyticsAssistant]

This pull request updates or adds the license line to the beginning of each Python file.

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Updated the license reference in all source files to explicitly mention "Ultralytics YOLOv5 🚀, AGPL-3.0 license".

📊 Key Changes

• Added "Ultralytics YOLOv5 🚀, AGPL-3.0 license" to the header of multiple source files, issue templates, workflows, and configuration files.

🎯 Purpose & Impact

• Purpose: To ensure consistent branding and licensing information across all files in the repository.
• Impact: Enhances clarity and consistency for users and contributors, making it clear that all components are part of the YOLOv5 project and governed by the same license.