feat: add Actions, OIDC export, and Grant management commands

New Commands:
- action: Manage Zitadel Actions (create, list, get, update, delete, deploy, undeploy)
- oidc: Export OIDC credentials for existing applications
- project grant: Manage project grants for multi-tenant scenarios
- user grant: Manage user role assignments (RBAC)

Client Methods Added:
- Action operations (12 methods)
- Project Grant operations (7 methods)
- User Grant operations (9 methods)

These are generic Zitadel features useful for:
- Multi-tenant SaaS applications
- Custom authentication flows
- Role-based access control
- OIDC application configuration

fix: address lint warnings and update test for token validation change

- Check fmt.Fprintln return value (errcheck)
- Add nolint:exhaustive for reflect.Kind switch
- Add nolint:gosec for CLI file path input
- Update test to reflect that token is now optional in New()

Co-Authored-By: Claude Opus 4.5 <[email protected]>

docs: fix markdown table formatting in README

Align table columns and fix minor whitespace issues.

fix: print error to stderr before exiting

SilenceErrors in Cobra suppresses error output, but the error
was not being printed anywhere. This made debugging failures
impossible.

Now errors are printed to stderr before exit code 1.

Merge pull request #1 from roylee17/feature/provision-enhancements

feat(provision): add extension, CLI app, custom roles, and K8s output

Initial commit: zitadel-cli