Implements workspace-scoped data isolation via subdomain routing:
- Schema: add workspaceSlug to Notebook model + migration
- Middleware: extract subdomain → x-workspace-slug header
- API: filter notebooks/notes/search by workspace on subdomains
- AppSwitcher: generate <username>.r*.online links when logged in
- Sessions: SubdomainSession component syncs auth across subdomains
via .rnotes.online domain-wide cookie
- Auth: auto-migrate unscoped notebooks to user's workspace
- New /api/me endpoint for client-side auth + workspace state
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
