v0.4.0

Changelog

• f012a49 Merge pull request #7 from gowtham-sai-yadav/feat/update-command
• f1e549b docs: document 'claude-teleport update' and refresh the Updating section
• dc82c15 feat(cli): add 'update' command; derive version from the git tag
• f12cc0b feat(updater): self-update package (check latest, verify checksum, swap binary)