feat(android): support API 24 setup-free

[tolgahan-arikan]

Summary

• Lower the Android wrapper defaults to minSdk 24 and Kotlin 2.1.20.
• Point Android at oms-client-kotlin-sdk:0.1.0-alpha.4 with coroutine/serialization versions aligned to the Kotlin SDK support branch.
• Update the Android bridge for Kotlin SDK string timestamps.
• Remove the Expo expo-build-properties minSdk workaround and update the standalone Expo example to the current OMSClient API.
• Update bare RN example Android defaults, docs, package version, changelog, and Expo lock metadata for 0.1.0-alpha.4.

Validation

• yarn lint
• yarn typecheck
• yarn test
• yarn sdk-example build:android
• yarn trails-actions-example build:android
• npm --prefix examples/expo-example ci
• npm --prefix examples/expo-example run typecheck
• Clean temp Expo proof using a packed local @0xsequence/oms-react-native-sdk@0.1.0-alpha.4 tarball:
  • npx expo prebuild --platform android --clean --no-install
  • generated Expo Android reported minSdk 24 and Kotlin 2.1.20
  • generated Expo Android had no expo-build-properties, coreLibraryDesugaring, or desugar_jdk_libs
  • ./gradlew :app:assembleDebug --no-daemon --console=plain --init-script /tmp/oms-e1-mavenlocal.gradle

Notes

This PR depends on io.github.0xsequence:oms-client-kotlin-sdk:0.1.0-alpha.4 from 0xsequence/kotlin-sdk#59 being published to Maven Central before this can be released. The local Expo npm ci passed because the 0.1.0-alpha.4 npm tarball was packed locally and available in the local npm cache; a clean environment needs the final npm publication flow for this same version.