docs: fix broken links flagged by the link checker

The CI markdown-link-check validates every link in the files touched by
the previous commit and reported three dead links, two of them
pre-existing in files this branch already modified:

- identity-federation-in-scs: the OpenStack Federation via OpenID-Connect
  link pointed at the old /dev-docs/ route, which now 404s; the section
  lives under /contributor-docs/.
- preinstall-checklist: the "are contributing" self-link used a malformed
  github.com/.../docs/docs/... path (404); point it at the blob/main URL.
- iaas landing page: https://ceph.io/ returns 500 to the checker; use
  https://www.ceph.io/en/, which resolves.

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Jan Klare <klare@osism.tech>

Author: jklare

contributor-docs/operations/iam/identity-federation-in-scs.md

@@ -21,7 +21,7 @@ The following sections describe how this is done.
 ## 1. IaaS / OpenStack
 
 To provide Infrastrucure as a Service SCS builds upon
-OpenStack. See section [OpenStack Federation via OpenID-Connect](https://docs.scs.community/dev-docs/operations/iam/openstack-federation-via-oidc)
+OpenStack. See section [OpenStack Federation via OpenID-Connect](https://docs.scs.community/contributor-docs/operations/iam/openstack-federation-via-oidc)
 for more details on identity federation for OpenStack.
 
 ## 2. CaaS

docs/01-getting-started/preinstall-checklist.md

@@ -27,7 +27,7 @@ of questions or a task list that should be discussed, clarified and processed in
 _Opensource benefits from the collaboration of its users and its developers._
 
 For this reason, we are collecting questions, important topics to be clarified and hints to make it easier for users of the Sovereign Cloud Stack to increase the success with it.
-Therefore we would be very pleased if specific experiences from users, implementers and operators [are contributing](https://github.com/SovereignCloudStack/docs/docs/01-getting-started/preinstall-checklist.md) to this list.
+Therefore we would be very pleased if specific experiences from users, implementers and operators [are contributing](https://github.com/SovereignCloudStack/docs/blob/main/docs/01-getting-started/preinstall-checklist.md) to this list.
 
 ## General
 

docs/02-iaas/index.md

@@ -8,7 +8,7 @@ sidebar_position: 1
 The SCS reference implementation of the Infrastructure-as-a-Service (IaaS) layer
 was built with [**OSISM**](https://osism.tech/docs). It builds on
 [OpenStack](https://openstack.org/) for compute, network and identity services and
-[Ceph](https://ceph.io/) for storage. The OpenStack deployment is based on
+[Ceph](https://www.ceph.io/en/) for storage. The OpenStack deployment is based on
 [Kolla](https://opendev.org/openstack/kolla) (container images) and
 [kolla-ansible](https://opendev.org/openstack/kolla-ansible), which OSISM wraps with
 additional Ansible playbooks and tooling to deploy and operate the whole stack.