feat(transaction): add transaction retrieval and DTO mapping

frontend/src/app/service/transaction.service.ts

@@ -0,0 +1,19 @@
+import { inject, Injectable } from '@angular/core';
+import { HttpClient } from '@angular/common/http';
+
+@Injectable({
+  providedIn: 'root',
+})
+export class TransactionService {
+  private http: HttpClient = inject(HttpClient);
+
+  public getUsersTransactions(limit: number|null = null) {
+    const baseUrl = '/backend/user/transactions';
+
+    if (limit !== null) {
+      return this.http.get<any[]>(`${baseUrl}?limit=${limit}`);
+    }
+
+    return this.http.get<any[]>(`${baseUrl}`);
+  }
+}