New users get sent to /join for passkey registration + auto-space-join.
Existing users are directly added with in-app + email notification.
Add-by-username now also sends email notification if email is on file.
- Add id to /api/users/lookup response
- Enhance /api/internal/user-email/:userId with recovery + profile email
- Add GET /api/internal/user-by-email for email→DID resolution
- Rewrite POST /:slug/invite to use identity invite flow
- Add email notification to POST /:slug/members/add
- Add success/error feedback to space settings invite UI
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>