docs: unify markdown files with documentation titles

This is preparational work to reduce the surface are of the different mappings

We want to reduce the following:

/guides/secrets.md -> Guides/getting started/How to use flakes with sops -> with '# Secrets Management'

- Title
- URI
- Filepath

should follow a stricter pattern to make it easy to maintain

docs/site/index.md

@@ -85,7 +85,7 @@ hide:
 
 ---
 
-[Get started](./guides/getting-started/index.md){ .md-button .md-button--primary }
+[Get started](/guides/getting-started/creating-your-first-clan){ .md-button .md-button--primary }
 [View on Gitea](https://git.clan.lol/clan/clan-core){ .md-button }
 
 ## Guides