feat(cabinet): legal footer on login + admin toggle

Adds a legal footer (Public Offer / Privacy / Recurring Payments) under the
login card, gated by CABINET_FOOTER_ENABLED (backend endpoint added in bot
PR #3011), plus an admin toggle in BrandingTab and ru/en/fa/zh i18n.

Footer-only subset of PR #464 — excludes the unrelated storePartnerClickId
helper and the version/CHANGELOG churn.

Co-authored-by: smediainfo <dev@matrixvpn.top>

src/components/LegalFooter.tsx

@@ -0,0 +1,46 @@
+import { Fragment } from 'react';
+import { useTranslation } from 'react-i18next';
+
+interface LegalLink {
+  href: string;
+  labelKey: string;
+  fallback: string;
+}
+
+const LINKS: LegalLink[] = [
+  { href: '/offer', labelKey: 'footer.offer', fallback: 'Публичная оферта' },
+  { href: '/privacy', labelKey: 'footer.privacy', fallback: 'Политика конфиденциальности' },
+  { href: '/recurrent-payments', labelKey: 'footer.recurrent', fallback: 'Рекуррентные платежи' },
+];
+
+interface LegalFooterProps {
+  className?: string;
+}
+
+export default function LegalFooter({ className = '' }: LegalFooterProps) {
+  const { t } = useTranslation();
+
+  return (
+    <footer
+      className={`flex flex-wrap items-center justify-center gap-x-2.5 gap-y-1 text-center text-[11px] leading-relaxed text-dark-500 ${className}`}
+    >
+      {LINKS.map((link, index) => (
+        <Fragment key={link.href}>
+          {index > 0 && (
+            <span className="text-dark-700" aria-hidden="true">
+              ·
+            </span>
+          )}
+          <a
+            href={link.href}
+            target="_blank"
+            rel="noopener noreferrer"
+            className="transition-colors hover:text-accent-400"
+          >
+            {t(link.labelKey, link.fallback)}
+          </a>
+        </Fragment>
+      ))}
+    </footer>
+  );
+}