fix: preflight Linux service manager

tests/release-scripts.test.sh

@@ -456,6 +456,19 @@ test_installer_requires_explicit_gitea_url() (
   [[ "$status" -ne 0 && "$output" == *'Gitea URL is required'* ]]
 )
 
+test_linux_service_preflight_requires_systemd() (
+  local tmp output status=0
+  tmp="$(mktemp -d "${TMPDIR:-/tmp}/erp-systemd-test.XXXXXX")" || return 1
+  trap 'rm -rf "$tmp"' EXIT
+  mkdir -p "$tmp/bin"
+  source "$PROJECT_ROOT/install.sh"
+  PLATFORM=linux
+  NO_SERVICE=0
+  output="$(PATH="$tmp/bin" validate_service_manager 2>&1)" || status=$?
+  [[ "$status" -ne 0 && "$output" == *'systemd'* ]] || return 1
+  NO_SERVICE=1 PATH="$tmp/bin" validate_service_manager
+)
+
 test_no_service_install_disables_online_update() (
   local tmp
   tmp="$(mktemp -d "${TMPDIR:-/tmp}/erp-no-service-test.XXXXXX")" || return 1
@@ -506,6 +519,7 @@ run_test 'update helper rolls back an unhealthy release end to end' test_update_
 run_test 'update helper rejects a concurrent process' test_update_lock_rejects_concurrent_process
 run_test 'installer moves database setup to the web wizard' test_installer_moves_database_setup_to_web_wizard
 run_test 'installer requires an explicit Gitea URL' test_installer_requires_explicit_gitea_url
+run_test 'Linux production install requires systemd' test_linux_service_preflight_requires_systemd
 run_test 'no-service install disables online update' test_no_service_install_disables_online_update
 run_test 'release workflow uses the scoped Gitea job token' test_release_workflow_uses_scoped_job_token
 run_test 'installer starts correctly when piped to bash' test_installer_runs_when_piped_to_bash