fix(ohos): add explicit ArkTS plugin types

[aozaoz112233]

Summary

Fix the HarmonyOS ArkTS build failure caused by strict arkts-no-any-unknown checks in ErikaFlutterPlugin.ets.

The affected expressions read ESObject values from Map<string, ESObject> or construct typed maps, but ArkTS inferred them as implicit any/unknown in the NipaPlay HarmonyOS build.

Changes

• Add explicit ESObject types to media metadata values.
• Add explicit Map<string, ESObject> types to copied/native argument maps.
• Add a regression contract test covering all affected declarations.
• Keep runtime behavior and the Flutter API unchanged.

Validation

• flutter test --no-pub --reporter expanded test/ohos_screenshot_contract_test.dart
  • 4 tests passed.
• Built NipaPlay from its current main branch with the fixed local Erika plugin:
  • Flutter 3.35.8-ohos-1.0.1
  • flutter build hap --release --no-pub --no-codesign --target-platform ohos-arm64
  • Build succeeded and produced a 133.9 MB unsigned HAP.
  • Verified the HAP contains both liberika_capi.so and liberika_flutter.so.

This fixes the failure seen in AimesSoft/NipaPlay-Reload Actions run 30883242192.

Compatibility

This change only touches the HarmonyOS ArkTS plugin implementation and its contract test. Android, iOS, macOS, Windows, and Linux code paths are unchanged.