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/app/i18n/translations.ts

@@ -520,6 +520,13 @@ export interface Translations {
     promptImageUrl: string;
     htmlEditorCode: string;
     htmlEditorPreview: string;
+    lastSaved: string;
+    draftRestored: string;
+    dismiss: string;
+    resetDraft: string;
+    resetSection: string;
+    confirmResetDraft: string;
+    confirmResetSection: string;
   };
   staticPages: {
     notFound: string;
@@ -553,6 +560,16 @@ export interface Translations {
     qrExpired: string;
     qrError: string;
   };
+  adminAuth: {
+    loginRequired: string;
+    loginDescription: string;
+    checking: string;
+    loginWithApp: string;
+    orScanQr: string;
+    loginNote: string;
+    qrExpired: string;
+    qrError: string;
+  };
   ux: {
     items: string;
     wishlistTitle: string;