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/app.config.ts

@@ -7,6 +7,9 @@ import { cacheInterceptor } from './interceptors/cache.interceptor';
 import { apiBaseUrlInterceptor } from './interceptors/api-base-url.interceptor';
 import { apiHeadersInterceptor } from './interceptors/api-headers.interceptor';
 import { mockDataInterceptor } from './interceptors/mock-data.interceptor';
+import { adminAuthHeadersInterceptor } from './core/admin-auth/admin-auth-headers.interceptor';
+import { Ed25519VerificationService } from './core/admin-auth/ed25519-verification.model';
+import { NoopEd25519VerificationService } from './core/admin-auth/noop-ed25519-verification.service';
 import { provideServiceWorker } from '@angular/service-worker';
 
 export const appConfig: ApplicationConfig = {
@@ -18,8 +21,9 @@ export const appConfig: ApplicationConfig = {
       withInMemoryScrolling({ scrollPositionRestoration: 'top' })
     ),
     provideHttpClient(
-      withInterceptors([mockDataInterceptor, apiBaseUrlInterceptor, apiHeadersInterceptor, cacheInterceptor])
+      withInterceptors([mockDataInterceptor, apiBaseUrlInterceptor, apiHeadersInterceptor, adminAuthHeadersInterceptor, cacheInterceptor])
     ),
+    { provide: Ed25519VerificationService, useClass: NoopEd25519VerificationService },
     provideServiceWorker('ngsw-worker.js', {
       enabled: !isDevMode(),
       registrationStrategy: 'registerWhenStable:30000'