feat: add legacy security warning API and UI modal for pre-factory-seal machines

Agent-Logs-Url: https://github.com/naturallaw777/staging_alpha/sessions/f7c8f11b-873b-403f-ac55-8b5b7cd9f1fb

Co-authored-by: naturallaw777 <99053422+naturallaw777@users.noreply.github.com>

app/sovran_systemsos_web/static/js/security.js

@@ -0,0 +1,23 @@
+"use strict";
+
+// ── Legacy security warning ───────────────────────────────────────
+
+function openSecurityWarningModal(message) {
+  if ($securityWarningMessage) $securityWarningMessage.textContent = message;
+  if ($securityWarningModal) $securityWarningModal.classList.add("open");
+}
+
+function closeSecurityWarningModal() {
+  if ($securityWarningModal) $securityWarningModal.classList.remove("open");
+}
+
+async function checkLegacySecurity() {
+  try {
+    var data = await apiFetch("/api/security/status");
+    if (data && data.status === "legacy") {
+      openSecurityWarningModal(data.warning || "This machine may have a known factory password. Please change your passwords immediately.");
+    }
+  } catch (_) {
+    // Non-fatal — silently ignore if the endpoint is unreachable
+  }
+}