feat(transaction-history): add transaction history feature with modal

frontend/src/app/feature/transaction-history/transaction-history.component.html

@@ -1 +1,10 @@
-<p>transaction-history works!</p>
+<div *ngIf="isOpen" [@fadeInOut] class="modal-bg" style="z-index: 1000; position: fixed;">
+  <div class="modal-card" [@cardAnimation]>
+    <h2 class="modal-heading">Transaktionen</h2>
+    <p class="py-2 text-text-secondary mb-4">Hier siehst du alle vergangenen Einzahlungen</p>
+    
+    <button type="button" (click)="closeDialog()" class="button-primary w-full py-2">
+      Verstanden
+    </button>
+  </div>
+</div>