v3.0.0 — SwiftPM support and New Architecture only

Breaking changes

• Removed React Native Old Architecture support. @preeternal/react-native-file-hash
  now requires the New Architecture and its TurboModule/codegen integration.
• Removed the deprecated positional overloads for fileHash and stringHash.
  Pass a request object as the second argument instead.
• Removed the deprecated hashString(...) alias; use stringHash(...).

Changed

• Updated the library template to create-react-native-library 0.63.0.
• Added iOS SwiftPM support for React Native 0.87. CocoaPods remains the default.
• Added the RN 0.87 examples/ExampleSpm app with a file picker and native
  benchmark-file module.
• SwiftPM selects one iOS engine at build time through React Native's SPM
  autolinking plugin. Set ZFHEngine=zig in the app's Info.plist to compile and
  link Zig; without the key it compiles and links only native. CocoaPods uses
  the build-time ZFH_ENGINE setting.
• Updated @react-native-documents/picker to v12.0.2 in example and patched its SwiftPM
  manifest.
• Grouped the project-owned iOS engine adapters under ios/Engines/Native and
  ios/Engines/Zig. The upstream implementations remain under third_party.
• Removed the old iOS bridge registration. FileHash is now registered through
  its generated TurboModule spec.
• Android now relies solely on the generated NativeFileHashSpec methods.

Fixed

• Android: Fix a Kotlin plugin conflict when building with AGP 9’s built-in Kotlin support enabled, while preserving compatibility with AGP 8.