feat: NCS-69 Challenge request (#3)

- create challange window
- challanges view page
- decline and accept
- notif tab (wip)
- active game window (wip)

---------

Co-authored-by: shahdlala66 <shahd.lala66@gmail.com>
Co-authored-by: Lala, Shahd <Shahd.Lala@sybit.de>
Reviewed-on: #3

src/app/components/challenge-notification/challenge-notification.component.html

@@ -0,0 +1,38 @@
+<div class="challenge-notification" [class.error]="!!errorMessage">
+    <div class="notification-header">
+        <div class="notification-title">
+            <span class="badge">CHALLENGE</span>
+            <span class="title">{{ getCreatedByDisplay() }} challenged you!</span>
+        </div>
+        <button type="button" class="close-btn" (click)="onClose()"
+            [disabled]="acceptingChallenge || decliningChallenge">
+            ×
+        </button>
+    </div>
+
+    <div class="notification-content">
+        <div class="time-control">
+            <span class="label">Time Control:</span>
+            <span class="value">{{ getTimeControlDisplay() }}</span>
+        </div>
+
+        <div class="expiration">
+            <span class="label">{{ getExpirationInfo() }}</span>
+        </div>
+
+        <div *ngIf="errorMessage" class="error-message">
+            {{ errorMessage }}
+        </div>
+
+        <div class="notification-actions">
+            <button type="button" class="btn btn-decline" (click)="onDecline()"
+                [disabled]="acceptingChallenge || decliningChallenge">
+                {{ decliningChallenge ? 'Declining...' : 'Decline' }}
+            </button>
+            <button type="button" class="btn btn-accept" (click)="onAccept()"
+                [disabled]="acceptingChallenge || decliningChallenge">
+                {{ acceptingChallenge ? 'Accepting...' : 'Accept' }}
+            </button>
+        </div>
+    </div>
+</div>