Add multi-arch amd64/arm64 container support

[vladbogun1]

Important

This patch was prepared by Codex AI, so I can't personally guarantee code quality or long-term maintainability yet.
I did, however, test it myself on my Oracle ARM host and confirmed that the server built, started, and worked there.

Summary

• add multi-arch container support for both linux/amd64 and linux/arm64
• keep the existing WineHQ path on amd64, and use Hangover on arm64 to run the Windows dedicated-server binary
• build repak and retoc natively for the target architecture instead of downloading x86_64-only helper binaries
• download the matching DepotDownloader build for the target architecture
• install pwsh on arm64 from the official PowerShell release tarball because the Debian 12 Microsoft apt repo does not provide a usable powershell package there
• remove the hard-coded platform: linux/amd64 from docker-compose.yml
• publish both linux/amd64 and linux/arm64 in the dev/release GitHub Actions workflows
• normalize shell scripts to LF during image build and add .gitattributes for *.sh to avoid CRLF entrypoint issues on Windows checkouts

Validation

• built the updated image successfully on a real arm64 Ubuntu host
• ran the container on that arm64 host and confirmed it became healthy
• confirmed the server installed successfully, generated ServerDescription.json, and started listening normally under the ARM compatibility path

Notes

• this keeps the upstream behavior unchanged for amd64
• the arm64 path still runs the original Windows dedicated-server build through a compatibility layer, so it is not a native ARM server binary