Add GitHub Actions workflow to build and push QM Docker image

[DKJKOH]

Purpose

Add a workflow to build the QM Docker image using deploy/core/Dockerfile and push both tags to Docker Hub.

Changes

• New workflow: .github/workflows/build-and-push-qm.yml
• Builds from deploy/core/Dockerfile
• Tags: docker.io/<username>/qm:latest and docker.io/<username>/qm:<short-sha>
• Triggered via workflow_dispatch (manual trigger in Actions UI)

How to use

1. Set repository secrets DOCKERHUB_USERNAME and DOCKERHUB_TOKEN (or pass them when triggering workflow_dispatch)
2. Go to Actions > Build and push QM Docker image > Run workflow
3. Optionally override username/token in workflow inputs
4. After completion, image digests will be in the job logs

Notes

• Uses docker/build-push-action@v4 for multiplatform build support
• Targets linux/amd64
• Short SHA is 7 characters from commit hash

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[time-attack]

Thanks for this, @DKJKOH — and sorry for the slow response.

We're closing this PR. Per CONTRIBUTING.md, since coding agents write most of the underlying code now, we'd rather receive feature ideas as a short human-written note in adrs/ — informal is great, just the idea in your own words — and bugs as a plain issue. If we're aligned we're happy to burn our own tokens on the implementation, and we'll credit you as co-author.

We don't want your idea to get lost, so we've captured it in #841 to triage on our side. Please feel free to open an adrs/ note if you feel strongly about the approach. Appreciate you engaging with the repo!