add screenshots for ios/flutter packages

[john-rocky]

app screenshots for iOS and Flutter packages.

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Adds a .gitignore rule to prevent macOS .DS_Store files from being committed 🧹🍎

📊 Key Changes

• Added a new .gitignore file that ignores .DS_Store (common macOS Finder metadata file) 🚫
• Updated several app screenshot image files (auto-generated/lock-related changes; diff not shown) 🖼️

🎯 Purpose & Impact

• Keeps the repo cleaner by avoiding accidental commits of OS-generated junk files ✅
• Reduces noisy PR diffs and unnecessary merge conflicts for contributors on macOS 🤝
• Screenshot updates ensure app visuals remain current, though changes are likely minor and asset-only 📸

📋 Skipped 4 files (lock files, generated, images, etc.)

• app/yolo-flutter-app/yolo-flutter-app-screenshot-detect.jpg
• app/yolo-flutter-app/yolo-flutter-app-screenshot-pose.jpg
• app/yolo-flutter-app/yolo-flutter-app-screenshot-segment.jpg
• app/yolo-ios-app/yolo-ios-app-screenshot.jpg

[UltralyticsAssistant]

👋 Hello @john-rocky, thank you for submitting an ultralytics/assets 🚀 PR! This is an automated response to help streamline the review process. An Ultralytics engineer will also assist you soon.

Please review the following checklist to ensure your contribution is ready for integration:

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