add openssh-client to devcontainer

[hacki11]

PR Checklist:

• Provide a meaningful description to this PR or mention which issues this fixes.
• Ensure the project builds with npm run build
• Add tests for your change. This includes negative tests (i.e. inputs that need to fail) as well as baseline tests (i.e. how should the directory structure look like?).
• Run the test suite with npm test
• If there are baseline changes, review them and make a separate commit for them with the comment "accept baselines" if they are desired changes
• N/A If you added a required option, also add it to the template creation (.github/create_templates.ts)
• Add a detailed migration description to docs/updates explaining what the user needs to do when manually updating an existing project
• Add your changes to CHANGELOG.md (referencing the migration description and this PR or the issue you fixed)

Description:
As a developer, I want to commit & push to the adapters git repository I cloned with a ssh url instead of https.
The current iobroker docker image does not include openssh-client, so ssh is not working. This PR changes that.

[hacki11]

How would you test such a change? Is there a test which validates that the DevContainer is actually working?

[hacki11]

@AlCalzone anything open from your side or can we merge this?

was done

[Copilot]

Pull Request Overview

Adds openssh-client to the devcontainer Docker image to enable SSH-based Git operations. This addresses a limitation where developers cannot commit and push to Git repositories cloned with SSH URLs because the base iobroker Docker image lacks SSH client support.

• Installs openssh-client package in the devcontainer Dockerfile
• Updates both template and baseline files to maintain consistency
• Provides migration documentation for existing projects

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
test/baselines/devcontainer/.devcontainer/iobroker/Dockerfile	Adds openssh-client installation to baseline Dockerfile
templates/_devcontainer/iobroker/_Dockerfile.ts	Updates template to include openssh-client installation
docs/updates/20250401_devcontainer_ssh.md	Provides migration guide for existing projects
CHANGELOG.md	Documents the change with reference to migration guide

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