Update license 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

Updating licensing comments to consistently reference "Ultralytics YOLOv3" in all project files.

📊 Key Changes

• Added "# Ultralytics YOLOv3 🚀, AGPL-3.0 license" comment to the top of all relevant source code files, scripts, and configuration files.
• Standardized the naming convention from "YOLOv3" or "YOLO" to "Ultralytics YOLOv3" across the entire codebase.

🎯 Purpose & Impact

• Consistency: Ensures all files clearly identify the software as "Ultralytics YOLOv3," which improves clarity and consistency.
• Licensing Clarity: Clearly states the AGPL-3.0 license, making it straightforward for users and developers to understand the licensing terms. This helps in maintaining transparency and compliance.
• Branding: Reinforces the Ultralytics brand association with the YOLOv3 model, enhancing brand recognition.

🚀 Overall, this makes the repository more professional and legally clear, which is beneficial for both internal development and external contributions.