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/css/security.css

@@ -0,0 +1,55 @@
+/* ── Legacy security warning modal ──────────────────────────────── */
+
+.security-warning-dialog {
+  max-width: 520px;
+}
+
+.security-warning-header {
+  background-color: #3b1212;
+  border-bottom-color: #7a2020;
+}
+
+.security-warning-body {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 16px;
+  padding: 24px 20px;
+}
+
+.security-warning-icon {
+  font-size: 2.5rem;
+}
+
+.security-warning-message {
+  text-align: center;
+  color: var(--text-primary);
+  line-height: 1.6;
+  margin: 0;
+}
+
+.security-warning-actions {
+  width: 100%;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 12px;
+}
+
+.security-warning-hint {
+  color: var(--text-secondary);
+  font-size: 0.85rem;
+  margin: 0;
+  text-align: center;
+}
+
+.security-warning-links {
+  display: flex;
+  gap: 12px;
+  flex-wrap: wrap;
+  justify-content: center;
+}
+
+.security-warning-link {
+  text-decoration: none;
+}