docs: add page explaining Euro-Office and Nextcloud Office builds

[juliusknorr]

Makes the difference between the Euro-Office community builds and Nextcloud Office clear, and points users to Nextcloud Office downloads.

Changes

• New Choose a build page under Installation comparing Nextcloud Office and Euro-Office, recommending Nextcloud Office for production
• Installation index:
  • Short explanation of Nextcloud Office vs Euro-Office
  • Download tables per OS for desktop apps and Document Server, in linked Nextcloud Office / Euro-Office tabs, with download, repository and documentation buttons
  • Note that the Document Server is not standalone and needs a platform such as Nextcloud
  • Nextcloud Office APT/DNF repository setup (download.nextcloud.com/office/repo)
  • Dropped "recommended for production" claims for the community builds
• Ubuntu, Debian and Fedora guides: Nextcloud Office repository tabs for adding the source, installing and updating
• Home page and overview link to the new page
• Styling: wider content area, full-width download tables, aligned table buttons

Repository setup tested on Ubuntu 24.04, Debian 12 and Fedora 44 containers (key import, metadata and package signatures).

Follow-ups

• Nextcloud Office Document Server container image (ghcr.io/nextcloud-releases/office-documentserver), currently "Coming soon"
  • feat: add nextcloud release workflow, put nextcloud office ssh push into separate step DocumentServer#421
• First release on nextcloud-releases/Office-DocumentServer, then switch download buttons to /releases/latest
  • feat: add nextcloud release workflow, put nextcloud office ssh push into separate step DocumentServer#421
• Rename desktop editor packages to nextcloud-office-desktopeditors DesktopEditors#146

Refs Euro-Office/DocumentServer#303, Euro-Office/DocumentServer#416

[chriscroome]

Thanks for the clarification, is Nextcloud going to charge for access to the Nextcloud deb/rpm repos and / or is a commercial support contract going to be needed to use the Nextcloud rather than the Euro-Office versions? What is the catch?

[juliusknorr]

No, we do not have any difference planned there. Signed builds and repositories are freely available for the community.