Move site content between installations as a package

System now exports a content package and imports one, by upload or from
var/pakete. Pages with their revisions, areas, menus, media, forms,
redirects, terms, translations, design and settings are replaced;
submissions, statistics, tasks, plugin state and service keys stay, and
accounts only come along when that is chosen explicitly. A backup comes
first, the site is in maintenance meanwhile, and every file and document
in the package is checked before anything is written.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/reset-huefner.sh

@@ -25,3 +25,7 @@ if [ -f "$root/var/cacert.pem" ]; then
 else
   "$php" bin/console cms:fonts:fetch
 fi
+# Das Inhaltspaket für die Live-Seite (ADR 118): dort unter System → Inhalte übertragen importieren.
+# Konten bleiben dabei, wie sie live sind.
+rm -f "$root/var/huefner-paket.zip"
+"$php" bin/console cms:paket:export --ziel="$root/var/huefner-paket.zip"