Add CAPIF provider integration to meep-app-enablement

- Add capif-client package with full provider lifecycle: login,
  user creation, auth, onboarding, publish/unpublish, and cleanup
- Support DNS override for CAPIF hostname resolution in Kubernetes
  (bypass /etc/hosts limitation with custom DialContext)
- Auto-publish MEC services to CAPIF on registration
- Unpublish all services on scenario teardown before provider offboarding
- Add CAPIF configuration env vars to Helm values-template
- Update entrypoint.sh with CAPIF hostname /etc/hosts fallback