feat(security): add enhanced cluster security analysis with container instance and capacity provider checks

- Add container instance security checks (agent version, connectivity, instance types)
- Add capacity provider security checks (termination protection, scaling config)
- Implement data collection methods for container instances and capacity providers
- Add comprehensive test coverage (94%) with 60+ new tests
- Follow color-coded severity pattern (🔴 High, 🟡 Medium, 🟢 Low)
- Include actionable CLI remediation steps for all recommendations

Closes #<issue-number>

Author: Suresh Natarajan