Add multi-arch builds for x86_64 and ARM64

[Copilot]

Implements automated cross-platform binary builds for x86_64 and ARM64 architectures. Docker images already supported multi-arch; this adds binary releases.

Changes

Release workflow (.github/workflows/release.yaml)

• Added upload-assets job with matrix strategy for cross-compilation
• Targets: Linux (x86_64, aarch64), macOS (x86_64, aarch64), Windows (x86_64)
• Uses taiki-e/upload-rust-binary-action for automated cross-compilation and GitHub Release uploads
• Triggered on version tags (v[0-9]+.*)

Documentation (README.md)

• Added "Supported Platforms" section listing all available binaries and architectures
• Reorganized "Getting Started" into subsections (source, Docker, pre-built binaries)
• Corrected Docker image reference to ghcr.io/prodzilla/prodzilla
• Clarified Docker multi-arch support (amd64, arm64)

Binary artifacts will be automatically published to GitHub Releases on the next tagged release.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Provide multi-arch builds for x86 and ARM</issue_title>
<issue_description>We need to implement automated builds that publish output for both x86_64 (amd64) and ARM64 architectures. This should cover all main release artifacts (including binaries and containers, if applicable). The build workflow should:

• Build and release for both x86 and ARM architectures
• Integrate into CI/CD so every commit/tag on main triggers builds for both
• Update documentation to clarify multi-arch support
• (If using Docker images) leverage Buildx for cross-arch publishing
• (If targeting binaries) ensure artifacts for both platforms are published in every release

Acceptance criteria:

• Both x86 and ARM artifacts are available for new releases
• Documentation is updated to make it clear multi-arch builds are supported
• Build jobs are green in CI

This will enable broader platform compatibility and future-proof our releases.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Provide multi-arch builds for x86 and ARM #42

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