chore(app-release): bump version to 0.3.0

[zhangjiadi225]

What this PR does

Updates the app version from 0.2.1 to 0.3.0 in app.json and the root package.json to prepare the next release.

Why we need it and why it was done in this way

Keeps both version declarations aligned with the planned v0.3.0 release tag. Native build numbers remain managed by EAS automatic increments.

After this PR is merged and CI passes, prepare the release notes and GitHub release draft before pushing the tag. The tag starts the existing release workflow for the GitHub APK, Google Play AAB artifact, and iOS TestFlight upload. GitCode publication and local artifact archival follow the successful builds.

Screenshots or videos

N/A — version metadata only.

Special notes for your reviewer

• pnpm lint passed with existing warnings in unchanged files.
• pnpm format and pnpm format:check passed.
• Local tests, type checking, and app builds were intentionally skipped under the user's verification policy; remote PR CI covers the test and type-check suites.
• Running pnpm format automatically invoked installation hooks, including regeneration of the document preview assets; no additional tracked files changed.

Release note

NONE