Add admin download and copy of markdown planning for all open tickets

## Summary As an admin user, it should be possible to download a planning of all open tickets. The planning will automatically group and order tickets logically, with detailed descriptions. The output is a markdown file rendered on the platform, with a download button and a copy-source button (using the existing renderer component, adding a copy button if missing, matching code-block style, enabled by default with an HTML attribute to disable). ## Steps to Reproduce Not provided. ## Expected Behaviour - Admin user can generate a planning of all open tickets. - Tickets are automatically grouped and placed in the most logical order. - The planning document includes a consistent, clear description of each ticket and the order. - The planning is rendered as markdown on the platform. - A button allows downloading the markdown file. - A button allows copying the markdown source directly. - The copy button uses the existing renderer component; if the renderer lacks a copy button, it should be added, identical to the one used for code blocks. - The copy button is built into the existing renderer component. - By default, the copy feature is enabled; it can be disabled via an HTML attribute. ## Actual Behaviour Not provided. ## Environment Not provided. --- *Reported by **retoor** via DevPlace.*