chore: add regenerate-catalog-docs.sh for future template additions

Whenever app-templates.js gains or changes a template, run this script
to keep /docs/catalog in sync. It generates all 78 static pages and
verifies the Next.js build still passes.

scripts/regenerate-catalog-docs.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+# Regenerate the /docs/catalog tree from the current
+# /opt/dashcaddy/dashcaddy-api/src/docker/app-templates.js.
+#
+# Run this whenever templates are added/changed. Outputs 78 static pages
+# under src/app/docs/catalog/ (1 index + 77 per-template).
+#
+# Idempotent — overwrites in place.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+node /tmp/generate-template-docs.js
+echo "Verifying build..."
+npx --no-install next build 2>&1 | tail -3
+echo "Done. Review with: git diff --stat src/app/docs/catalog/"