fix(auth): make login footer legal links open real pages, not the login tab

The login-page footer linked to /offer, /privacy and /recurrent-payments with
target=_blank, but none of those routes existed, so opening them hit the SPA
catch-all, which redirects unauthenticated users to /login — every footer link
just opened another login tab.

- Add a public PublicLegal page that fetches the offer / privacy document from the
  existing public /cabinet/info endpoints and renders sanitized HTML (DOMPurify via
  the shared formatContent helper).
- Register public /offer and /privacy routes.
- Extract sanitizeHtml/formatContent into src/utils/legalContent.ts and reuse from
  Info.tsx (was duplicated).
- Drop the /recurrent-payments footer link: there is no recurring-payments legal
  document or endpoint in the backend, so it had no real destination. Re-add once
  such a document exists.

type-check, eslint, prettier and build all pass.

src/locales/en.json

@@ -4779,6 +4779,7 @@
     "loyalty": "Loyalty",
     "noFaq": "No FAQ available",
     "noContent": "No content available",
+    "documentUnavailable": "This document is not available yet.",
     "updatedAt": "Updated",
     "noLoyaltyTiers": "Loyalty program is not available yet",
     "yourProgress": "Your Progress",