fix: resolve merge conflicts with master for 6.17.9-rc1

- Keep 6.17.9-rc1 version across pubspec.yaml, podspec, README
- Keep Android SDK 6.17.6 and iOS SDK 6.17.9 version bumps
- Keep UIScene fixes in AppsflyerSdkPlugin.h and .m
- Keep improved promote-release.yml workflow from release branch

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Kobikg78