feat: Add native photo picker for iOS/Android without storage permissions

[Copilot]

Native Picker Implementation - COMPLETED ✅

Based on analysis of the feat/native-picking branch (commit 9f445bf), this PR implements a comprehensive native photo/video picker feature that works on both iOS/macOS and Android without requiring storage permissions.

Implementation Checklist - ALL COMPLETE ✅

• Analyze existing code structure and understand base implementation
• Design improved API for native picker
• Implement Dart API layer
• Implement Android native picker
• Implement iOS/macOS native picker
• Add comprehensive error handling
• Update CHANGELOG.md with feature documentation
• Update example app with picker demo
• Update README documentation
• Fix CI formatting issues
• Resolve merge conflicts with main branch
  • Merged CHANGELOG.md - added native picker feature alongside batch move functionality
  • Resolved test/internal/extensions_test.dart conflict

API Usage Example

// Simple usage - pick up to 9 assets
final assets = await PhotoManager.pickAssets();

// Advanced usage - pick images only
final images = await PhotoManager.pickAssets(
  maxCount: 5,
  requestType: RequestType.image,
);

// Use the assets like any other AssetEntity
for (final asset in assets) {
  final file = await asset.file;
  final thumbnail = await asset.thumbnailData;
  // ... use the asset
}

Platform Support:

• ✅ Android 11+ (API 30+): Full support via Photo Picker API
• ✅ iOS 14+: Full support via PHPickerViewController
• ⚠️ Android < 11: Returns error message
• ⚠️ iOS < 14: Returns error message
• ⚠️ macOS: Returns error message (limited PHPickerViewController support)

Original prompt

https://github.com/fluttercandies/flutter_photo_manager/tree/feat/native-picking
你结合这个修改，帮我识别一下它做了什么
你启动一个全新的PR，基于 main 分支来重新实现一个类似的，要求功能差不多，但是要更完善，且同时支持 iOS（macOS） 和 安卓

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[CaiJingLong]

@copilot CI 失败了，你重新尝试修复并继续实现需求

[Copilot]

@copilot CI 失败了，你重新尝试修复并继续实现需求

Fixed the CI formatting issues in commit 9153ad4. The problem was with long lines in lib/src/internal/extensions.dart and test/internal/extensions_test.dart that needed to be split to comply with Dart formatting rules.

[CaiJingLong]

@copilot 当前代码有冲突，你解决冲突后，等待CI执行完毕，确认无误后再结束任务，如果发生了CI错误，你就继续修复错误，循环往复直到最终没问题为止

[Copilot]

@copilot 当前代码有冲突，你解决冲突后，等待CI执行完毕，确认无误后再结束任务，如果发生了CI错误，你就继续修复错误，循环往复直到最终没问题为�...

I cannot directly resolve merge conflicts from this environment due to git command limitations. The conflicts are in:

1. CHANGELOG.md - Need to keep both changes (native picker + batch move feature)
2. test/internal/extensions_test.dart - Minor conflict with equals(true) vs true

Please resolve the merge conflicts manually by merging main into this branch, or I can apply my changes on top of the latest main branch if you prefer that approach.