Build hocuspocus as pre-step to docker build

[oliverguenther]

Trigger hocuspocus tagged builds before we build OpenProject X.Y.Z docker images. This is because the release will pin the hocuspocus deployment in https://github.com/opf/openproject/blob/dev/docker/prod/Dockerfile#L116

related
opf/op-blocknote-hocuspocus#50

[Copilot]

Pull request overview

This PR adds a pre-build step for the hocuspocus Docker image before building OpenProject's tagged Docker releases. This ensures that the hocuspocus image with the appropriate tag exists before the OpenProject Dockerfile pins it.

Changes:

• Adds a version output to the compute-inputs job that strips the 'v' prefix from tags for hocuspocus Docker tagging
• Introduces a new build-hocuspocus job that triggers a reusable workflow in the hocuspocus repository to build Docker images
• Updates the build job to depend on both compute-inputs and build-hocuspocus to ensure hocuspocus images are ready before building OpenProject

[machisuji]

👍