docs: Add admin client documentation and examples

- Add comprehensive admin_client_guide.md with usage patterns and
best practices
- Add complete API reference in docs/api/admin_api.md
- Add 3 example scripts: simple_register.py, deploy_monitor.py,
manifest_generation.py
- Add examples README with usage instructions
- Cover all major workflows: registration, deployment, monitoring,
manifest generation
- Include error handling patterns and integration examples

Author: fordN