CI skips build, tests and deploy for docs-only changes

**What:** Markdown, `docs/` and `cds_docs_femhealth/` changes no longer run the build, full suite or deploy. `pr-gate` still reports a result, so docs-only PRs aren't stuck on required checks.
**Evidence:** the filter classifies #477 (ReadTheDocs) as docs-only.
**Fix:** DataSpaceFrontend#478 (dev), #479 (main).
