fix(admin-auth): reuse exact same QR/session API and component for admin login

- Removed invented adminAuthApiUrl endpoint and separate AdminLoginComponent.
  Admin login now uses the exact same Telegram session backend
  (TelegramSessionApiService, {authApiUrl}/users/sessions) and the exact
  same TelegramLoginComponent (mode="customer" | "admin" input) as customer
  login - only the storage (cookie/localStorage/signals) stays separate.
- Extracted the shared HTTP+normalization logic from AuthService into
  TelegramSessionApiService so both AuthService and AdminAuthService call it
  instead of duplicating request/parsing code.
- Documented the resulting backend gap in docs/Project-Editor.md: since the
  session API has no concept of "admin", server-side role enforcement is
  required when admin API calls are made - the frontend only decides where
  to store the session, not whether the user is actually an admin.

src/app/app.ts

@@ -15,13 +15,13 @@ import { PlatformRuntimeService } from './core/runtime/platform-runtime.service'
 import { UiRuntimeFacade } from './facades/runtime/ui-runtime.facade';
 import { ApiHealthService } from './services/api-health.service';
 import { FloatingNotificationsComponent } from './features/website/user-experience/components/floating-notifications/floating-notifications.component';
-import { AdminLoginComponent } from './core/admin-auth/admin-login.component';
 import { AdminAuthService } from './core/admin-auth/admin-auth.service';
 import { AuthService } from './services/auth.service';
+import { TelegramLoginComponent } from './components/telegram-login/telegram-login.component';
 
 @Component({
   selector: 'app-root',
-  imports: [RouterOutlet, HeaderComponent, FooterComponent, BackButtonComponent, TranslatePipe, FloatingNotificationsComponent, AdminLoginComponent],
+  imports: [RouterOutlet, HeaderComponent, FooterComponent, BackButtonComponent, TranslatePipe, FloatingNotificationsComponent, TelegramLoginComponent],
   templateUrl: './app.html',
   styleUrl: './app.scss'
 })