feat(frontend): wire notification component into dashboard header

- Import NotificationComponent in DashboardLayout
- Add bell icon with unread badge to dashboard header

eeg_frontend/src/app/layout/dashboard-layout/dashboard-layout.html

@@ -50,6 +50,7 @@
       </h1>
 
       <div class="flex items-center gap-4">
+        <app-notification />
         <span class="text-sm text-gray-500 hidden sm:inline">
           Rolle: <span class="font-semibold text-gray-700">{{ authService.currentUserRole() }}</span>
         </span>

eeg_frontend/src/app/layout/dashboard-layout/dashboard-layout.ts

@@ -2,11 +2,12 @@ import {Component, computed, inject, signal} from '@angular/core';
 import {Router, RouterLink, RouterLinkActive, RouterOutlet} from '@angular/router';
 import {AuthService} from '../../services/auth';
 import {NAV_ITEMS} from './dashboard-nav-items';
+import {NotificationComponent} from '../../components/notification/notification';
 
 @Component({
   selector: 'app-dashboard-layout',
   standalone: true,
-  imports: [RouterOutlet, RouterLink, RouterLinkActive],
+  imports: [RouterOutlet, RouterLink, RouterLinkActive, NotificationComponent],
   templateUrl: './dashboard-layout.html',
   styleUrl: './dashboard-layout.scss'
 })