Task/eliminate OnDestroy lifecycle hook from open page component

Replace manual Subject-based teardown with Angular's built-in
DestroyRef and takeUntilDestroyed from @angular/core/rxjs-interop.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/client/src/app/pages/open/open-page.component.ts

@@ -7,11 +7,11 @@ import {
   ChangeDetectorRef,
   Component,
   CUSTOM_ELEMENTS_SCHEMA,
-  OnDestroy,
+  DestroyRef,
   OnInit
 } from '@angular/core';
+import { takeUntilDestroyed } from '@angular/core/rxjs-interop';
 import { MatCardModule } from '@angular/material/card';
-import { Subject, takeUntil } from 'rxjs';
 
 @Component({
   host: { class: 'page' },
@@ -21,15 +21,14 @@ import { Subject, takeUntil } from 'rxjs';
   styleUrls: ['./open-page.scss'],
   templateUrl: './open-page.html'
 })
-export class GfOpenPageComponent implements OnDestroy, OnInit {
+export class GfOpenPageComponent implements OnInit {
   public statistics: Statistics;
   public user: User;
 
-  private unsubscribeSubject = new Subject<void>();
-
   public constructor(
     private changeDetectorRef: ChangeDetectorRef,
     private dataService: DataService,
+    private destroyRef: DestroyRef,
     private userService: UserService
   ) {
     const { statistics } = this.dataService.fetchInfo();
@@ -39,7 +38,7 @@ export class GfOpenPageComponent implements OnDestroy, OnInit {
 
   public ngOnInit() {
     this.userService.stateChanged
-      .pipe(takeUntil(this.unsubscribeSubject))
+      .pipe(takeUntilDestroyed(this.destroyRef))
       .subscribe((state) => {
         if (state?.user) {
           this.user = state.user;
@@ -48,9 +47,4 @@ export class GfOpenPageComponent implements OnDestroy, OnInit {
         }
       });
   }
-
-  public ngOnDestroy() {
-    this.unsubscribeSubject.next();
-    this.unsubscribeSubject.complete();
-  }
 }