ci(docs): add markdownlint foundation (prek + CI) (#11210)

Co-authored-by: Pablo F.G <pablo.fernandez@prowler.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.markdownlintignore

@@ -0,0 +1,16 @@
+node_modules/
+ui/node_modules/
+.git/
+.venv/
+**/.venv/
+dist/
+build/
+htmlcov/
+.next/
+ui/.next/
+ui/out/
+contrib/
+
+# Auto-generated content (keepachangelog format legitimately repeats section headings).
+# Revisit with the team — see beads task on markdownlint rule triage.
+**/CHANGELOG.md