feat: add New-API offline run package builders

[yuanyp8]

Summary

Adds an offline .run delivery project for New-API with two independent package types:

• Docker Compose package: packages/compose
• Kubernetes package: packages/k8s

The GitHub Actions workflow builds both amd64 and arm64 artifacts and publishes .run plus .sha256 files. Tag pushes matching v* publish the artifacts to GitHub Release.

What is included

• Multi-arch GitHub Actions workflow
• Shared offline package build library
• Compose installer package
• Kubernetes installer package
• Image manifest metadata
• Runtime installers with image load/tag/push, registry retargeting, status, and uninstall actions

Validation done

• Local shell syntax check for generated scripts before pushing
• Local JSON validation for image manifests before pushing
• Repository diff checked after pushing

Notes

The current CI builds the New-API application image from upstream source during Actions. This packaging repo does not vendor the complete upstream New-API source tree. Kubernetes deployment is a basic single-replica offline delivery baseline with PostgreSQL and Redis bundled as workloads.