- UserRole enum: Admin (full), Viewer (read-only), AppUser (minimal)
- can_access() method checks RPC method against role permissions
- Role field on User struct with serde default (backward-compatible)
- Viewer: read system/federation/DWN/identity/backup/container status
- AppUser: system.stats, node.did, container list, password change
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>