feat: prompt for bootstrap enrollment authorization

scripts/modules/12_enrollment_auth.sh

@@ -35,7 +35,15 @@ prepare_runtime_directory() {
 store_bootstrap_authorization() {
     local activation_code
 
-    activation_code="${TUXFLOTTE_ACTIVATION_CODE:-LAB-2026-START}"
+    if [[ -n "${TUXFLOTTE_ACTIVATION_CODE:-}" ]]; then
+        activation_code="${TUXFLOTTE_ACTIVATION_CODE}"
+    else
+        printf '\n'
+        read -r -p "Temporären Aktivierungscode eingeben: " activation_code
+    fi
+
+    [[ -n "${activation_code}" ]] ||
+        fatal "Es wurde kein Aktivierungscode angegeben."
 
     jq \
         --null-input \