Use runtime app metadata for version reporting

[jjoonleo]

Summary

• Add an injectable PackageInfo-backed app metadata provider.
• Use the injected runtime app version for Product Usage Event app_version parameters.
• Use the same metadata source for AlarmDeviceInfo.appVersion during alarm device registration.
• Add regression coverage for the metadata provider, analytics event parameters, and alarm device payloads.

Test results

• dart run build_runner build --delete-conflicting-outputs
• flutter test test/core/services/app_metadata_service_test.dart test/core/services/product_analytics_service_test.dart test/data/repositories/alarm_repository_impl_test.dart test/presentation/app/cubit/analytics_preference_cubit_test.dart test/presentation/my_page/my_page_screen_test.dart
• flutter analyze

Closes #546