Add release workflow with beta support to publish to GitHub Container Registry

[Copilot]

• Add beta release support to release workflow (stable → 1.2.3, 1.2, latest; pre-release → 1.2.3-beta.1, beta)
• Extract pre-release detection into a named step output for maintainability
• Update README to document beta image usage
• Fix Docker build failure: remove /etc/apt/sources.list.d/yarn.list (expired GPG key in base image) before apt-get update

Original prompt

We're making a devcontainer to be used by Home Assistant custom card developers. We can use this repo as a starting point: https://github.com/thomasloven/hass-custom-devcontainer
We do not need to support plugins. I want to use the latest version of home assistant. Be smarter about downloading and creating the HACS integration. Ideally we'd only do it if there's a newer version of HACS to pull down. Also, support remote files using this PR I submitted thomasloven/hass-custom-devcontainer#231. In general though, look for any areas for performance updates, updates to libraries used and make sure this is portable and usable within Github workspaces as well.

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[iantrich]

@copilot I'm getting the following error in the release workflow with this code

ERROR: failed to build: failed to solve: process "/bin/bash -o pipefail -c apt-get update     && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends         bluez         libffi-dev         libssl-dev         libjpeg-dev         zlib1g-dev         autoconf         build-essential         libopenjp2-7         libtiff6         libturbojpeg0-dev         tzdata         ffmpeg         liblapack3         liblapack-dev         libatlas-base-dev         git         libpcap-dev         unzip     && apt-get clean     && rm -rf /var/lib/apt/lists/*     && source /usr/local/share/nvm/nvm.sh     && nvm install --lts     && pip install --upgrade wheel pip uv" did not complete successfully: exit code: 100
Reference
Check build summary support
Error: buildx failed with: ERROR: failed to build: failed to solve: process "/bin/bash -o pipefail -c apt-get update     && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends         bluez         libffi-dev         libssl-dev         libjpeg-dev         zlib1g-dev         autoconf         build-essential         libopenjp2-7         libtiff6         libturbojpeg0-dev         tzdata         ffmpeg         liblapack3         liblapack-dev         libatlas-base-dev         git         libpcap-dev         unzip     && apt-get clean     && rm -rf /var/lib/apt/lists/*     && source /usr/local/share/nvm/nvm.sh     && nvm install --lts     && pip install --upgrade wheel pip uv" did not complete successfully: exit code: 100

https://github.com/custom-cards/custom-card-devcontainer/actions/runs/22604654914/job/65493981529

[Copilot]

@copilot I'm getting the following error in the release workflow with this code

ERROR: failed to build: failed to solve: process "/bin/bash -o pipefail -c apt-get update     && DEBIAN_FRONTEND=n...

The failure was caused by the base image (mcr.microsoft.com/devcontainers/python:1-3.13) shipping with /etc/apt/sources.list.d/yarn.list, whose GPG key has expired — making apt-get update exit with code 100.

Since Node.js is already installed via nvm, the Yarn apt-source isn't needed. Fixed in b792c47 by removing that file before running apt-get update:

RUN rm -f /etc/apt/sources.list.d/yarn.list \
    && apt-get update \
    ...