Adds `hf user reset-apikey <username>` to regenerate a user API key.
Requires user.manage permission. Returns the new key (shown once only).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
- Add internal/commands/user.go with full user CRUD implementation
- Wire user subcommands in main.go dispatch
- Mark user subcommands as Permitted: true
- Support both padded-cell and manual mode for all user commands
- user create uses account-manager token flow per plan
