feat(auth): add login and registration modal functionality

frontend/src/app/feature/auth/register/register.component.html

@@ -1,5 +1,16 @@
 <div class="min-h-screen bg-deep-blue flex items-center justify-center">
-  <div class="modal-card max-w-md w-full">
+  <div class="modal-card max-w-md w-full bg-deep-blue rounded-lg shadow-xl p-6 relative">
+    <!-- Close Button -->
+    <button 
+      (click)="closeDialog.emit()"
+      class="absolute top-4 right-4 text-text-secondary hover:text-white transition-colors"
+      aria-label="Dialog schließen"
+    >
+      <svg xmlns="http://www.w3.org/2000/svg" class="h-6 w-6" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M6 18L18 6M6 6l12 12" />
+      </svg>
+    </button>
+
     <h2 class="modal-heading text-center">Konto erstellen</h2>
 
     @if (errorMessage()) {
@@ -107,12 +118,12 @@
     <div class="mt-6 text-center">
       <p class="text-sm text-text-secondary">
         Bereits ein Konto?
-        <a
-          routerLink="/login"
+        <button
+          (click)="switchToLogin()"
           class="font-medium text-emerald hover:text-emerald-light transition-all duration-200"
         >
           Anmelden
-        </a>
+        </button>
       </p>
     </div>
   </div>