✨ Feat: add model-downloader service with init container integration

[samzong]

FILL IN THE PR DESCRIPTION HERE

FIX #678 (link existing issues this PR will resolve)

Support a dedicated multi-arch model-downloader image (Dockerfile + workflow wiring)

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👥 vLLM Semantic Team Notification

The following members have been identified for the changed files in this PR and have been automatically assigned:

📁 Root Directory

Owners: @rootfs, @Xunzhuo
Files changed:

• Dockerfile.model-downloader
• .github/workflows/docker-publish.yml

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🎉 Thanks for your contributions!

This comment was automatically generated based on the OWNER files in the repository.

[samzong]

@rootfs @Xunzhuo

It seems that the reason CI fails is because there is no mirror (the first build has not been merged yet). Is there any solution suggestion?

[samzong]

I think it's can be split to 2 PRs.

Currently forcing build image and pushlish image.

Then upgrade helm chart.