ci-health-check.sh: append infra as private repo after dynamic discovery

Adds 'infra' to PLUGIN_REPOS after the discovery/fallback logic so the
private infra repo is always included in CI/CD health checks regardless
of which path populated PLUGIN_REPOS.

Fixes: PRI-906
Fixes: PRI-488

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.github/scripts/ci-health-check.sh

@@ -44,6 +44,9 @@ if [ ${#PLUGIN_REPOS[@]} -eq 0 ]; then
   PLUGIN_REPOS=("${PLUGIN_REPOS_FALLBACK[@]}")
 fi
 
+# Private repos not visible to dynamic discovery
+PLUGIN_REPOS+=("infra")
+
 echo "=== CI/CD Health Check — $(date -u '+%Y-%m-%d %H:%M UTC') ==="
 echo ""