docs: fix broken links and anchors across documentation

Fix ~30 broken links and anchors across the documentation site, including
incorrect relative paths, mismatched anchor names, zero-width characters
in URLs, and references to renamed or removed headings.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Fredrik Adelöw <freben@spotify.com>

docs/publishing.md

@@ -47,12 +47,12 @@ Additional steps for the main line release
   - Check for mentions of "major" & "breaking" and if they are expected in the current release
   - Verify the version we are shipping is correct
 - Create Release Notes
-  - There exists a [release notes template](./.release-notes-template.md) for creating the release notes. It can already be created after the last main line release to keep track of major changes during the month
+  - There exists a release notes template (`.release-notes-template.md`) for creating the release notes. It can already be created after the last main line release to keep track of major changes during the month
   - The content is picked by relevancy showcasing the work of the community during the month of the release
   - Mention newly added packages or features
   - Mention any security fixes
 - Create Release Notes PR
-  - Add the release note file as [`/docs/releases/vx.y.0.md`](./releases)
+  - Add the release note file as [`/docs/releases/vx.y.0.md`](https://backstage.io/docs/releases/)
   - Finally copy the content, without the metadata header, into the description of the [`Version Packages` Pull Request](https://github.com/backstage/backstage/pulls?q=is%3Aopen+is%3Apr+in%3Atitle+%22Version+Packages)
 
 Once the release has been published edit the newly created release in the [GitHub repository](https://github.com/backstage/backstage/releases) and replace the text content with the release notes.