Split GitHub Actions workflow to publish separate app and web Docker images

[henmohr]

Motivation

• Separate the app and web components so each image can be built, tagged and published independently.
• Use distinct build contexts and image names to simplify lifecycle and enable different release cadences for the app and web images.

Description

• Introduce IMAGE_NAME_APP and IMAGE_NAME_WEB environment variables and update the registry image names to use those suffixes.
• Add meta_app and meta_web metadata extraction steps using docker/metadata-action@v5 and consume their outputs for tagging and labeling.
• Split the build into two docker/build-push-action@v6 steps with contexts set to .docker/app and .docker/web respectively, preserving cache-from and cache-to settings.
• Rename and clarify step names so tags and labels are sourced from the corresponding metadata outputs.

Testing

• No automated tests were run for this change because it only modifies a CI workflow; the updated workflow will be exercised by CI on the next push or pull request.

---

Codex Task