feat(sprint18): editor autosave/reset, admin auth, QR reuse, Ed25519 prep

- Project editor: persist draft to localStorage, restore on reload,
  last-saved/draft-restored status indicators, section/whole-draft reset
  with confirmation.
- Extract shared QR/polling/expiry engine from TelegramLoginComponent
  (shared/qr-login) and reuse it for a new admin login flow.
- Admin authentication kept fully separate from customer session:
  own cookie/localStorage keys, signals, guard, and header interceptor
  (core/admin-auth).
- ?login=true / ?adminLogin=true open the respective login dialog for
  manual testing.
- Ed25519 challenge/verify interfaces (fail-closed no-op binding) ready
  for backend delivery.
- Document autosave/reset/admin-auth/QR-reuse/Ed25519 model and the
  remaining full-field-coverage gap in docs/Project-Editor.md.

src/environments/environment.production.ts

@@ -15,6 +15,8 @@ export const environment = {
   theme: 'dexar',
   apiUrl: 'https://api.dexarmarket.ru:445',
   authApiUrl: 'https://users.vitanova.network:456',
+  // Placeholder until backend delivers dedicated admin auth endpoints - keep path-scoped under authApiUrl so it's easy to repoint.
+  adminAuthApiUrl: 'https://users.vitanova.network:456/admin',
     qrApiUrl: 'https://qr.vitanova.network/api',
   logo: '/icons/icon-192x192.png',
   contactEmail: 'info@dexarmarket.ru',