feat: add native Android, iOS, and HarmonyOS app scaffolds

[wgqqqqq]

Summary

• add a native mobile app boundary under src/apps/mobile
• add initial Android and iOS source/resource directory scaffolds
• import the existing HarmonyOS phone client, including ArkTS UI, remote-session services, resources, tests, OHPM/Hvigor configuration, and a fake relay development tool
• keep local signing credentials, build outputs, dependencies, screenshots, and development caches out of the repository

Type and Areas

Type: Feature

Areas: Native mobile apps, HarmonyOS, Android, iOS

Motivation / Impact

This establishes repository-owned entrypoints for native mobile clients. The HarmonyOS project can now be developed and built from this repository, while Android and iOS have explicit ownership boundaries ready for implementation.

Verification

• pnpm run check:repo-hygiene - passed
• git diff --check - passed
• source scripts/ohos-env.sh && "$OHPM" install - passed
• source scripts/ohos-env.sh && "$HVIGORW" --mode module -p module=entry assembleHap --no-daemon - build successful
• scanned the imported project for signing credentials, private keys, and user-specific absolute paths - no matches

The HarmonyOS compiler reports existing warnings for throwable APIs and deprecated APIs, but no compilation errors.

Reviewer Notes

• HarmonyOS targets 6.1.1(24) and supports 6.0.1(21) or newer.
• Signing configuration is intentionally omitted. Developers must configure a local signing identity in DevEco Studio for device installation.
• Android and iOS contain directory scaffolds only; no native toolchain or dependencies are introduced yet.
• AI-assisted change. Testing level: repository hygiene checks plus a local HarmonyOS dependency install and full unsigned HAP build.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.