fix: close auth callback server after login

[jlitola]

Summary

• Close the OAuth callback server immediately after successful login callbacks so auto-login CLI commands can exit promptly.
• Bump package patch version to 0.4.2.
• Add regression coverage for closing the callback server on the successful login path.

Verification

• bun test src/commands/login.test.ts src/services/auth-service.test.ts
• bun run typecheck
• bun run smoke:cli