fix(install): fix Debian 13 LXC template root ownership bug

The Debian 13 LXC template has a bug where / is owned by nobody instead
of root. This causes systemd-tmpfiles to fail with exit code 73 during
package installation (e.g. authelia).

Fix by checking and correcting / ownership at container setup.

misc/install.func

@@ -79,6 +79,13 @@ EOF
 # ------------------------------------------------------------------------------
 setting_up_container() {
   msg_info "Setting up Container OS"
+
+  # Fix Debian 13 LXC template bug where / is owned by nobody
+  # Only attempt in privileged containers (unprivileged cannot chown /)
+  if [[ "$(stat -c '%U' /)" != "root" ]]; then
+    chown root:root / 2>/dev/null || true
+  fi
+
   for ((i = RETRY_NUM; i > 0; i--)); do
     if [ "$(hostname -I)" != "" ]; then
       break