Add frontend and Tauri command test coverage

[devin-ai-integration]

The verify step in DEVELOPMENT.md (lines ~431-438) only runs npm run build for the desktop UI with no automated frontend tests.

Problem

• No automated frontend test coverage; the verify step only builds.

Suggested direction

• Add React component / integration tests.
• Add end-to-end coverage of the Tauri commands.

References

• DEVELOPMENT.md (lines ~431-438)