Build Docker image for multiple platforms (amd64 and arm64)

[adamtheturtle]

The Docker image was only being built for linux/amd64, which doesn't work on ARM machines (including Apple Silicon Macs).

This adds platforms: linux/amd64,linux/arm64 to the Docker build step so the image works on both architectures.

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Note

Publishes Docker images for multiple architectures in the release workflow.

• In .github/workflows/release.yml, sets docker/build-push-action platforms to linux/amd64,linux/arm64 to push a multi-arch image to GHCR
• No application code changes; only CI/release pipeline affected

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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Missing QEMU setup for cross-platform Docker build

High Severity

Adding platforms: linux/amd64,linux/arm64 for multi-platform Docker builds requires docker/setup-qemu-action to be run before docker/setup-buildx-action. Without QEMU emulation setup, the ARM64 build will fail on the AMD64 GitHub runner. Docker's official documentation and the setup-buildx-action README state that QEMU setup is required for cross-architecture emulation support.