Adds .devcontainer/devcontainer.json that points to Dockerfile.dev so any
devcontainer-aware tool (VS Code, Codespaces, etc.) can build the local
dev environment directly from source.
Adds a Forgejo workflow that rebuilds and pushes the image to
codeberg.org/guettli/sharedinbox-dev (tagged both :latest and the short
commit SHA) whenever Dockerfile.dev, the devcontainer config, or the
workflow itself changes on main. This prevents the published image from
silently drifting from its source.
The workflow uses the built-in FORGEJO_TOKEN to log in to the Codeberg
container registry - no extra secrets needed.
Closes#552
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
