Implement full pagination support for task fetching

Refactored the TaskService and TaskViewModel classes to fully support paginated fetching of tasks. The solution fetches tasks page by page until all tasks have been retrieved, accommodating the API's pagination mechanism. Renamed `listAllTasks` to `fetchTasksPage` to better reflect its purpose and introduced a new method, `fetchAllTasks`, to handle the paginated fetching logic.

frontend/lib/services/task_service.dart

@@ -1,3 +1,4 @@
+import 'package:auto_gpt_flutter_client/models/task.dart';
 import 'package:auto_gpt_flutter_client/models/task_request_body.dart';
 import 'package:auto_gpt_flutter_client/models/task_response.dart';
 import 'package:auto_gpt_flutter_client/utils/rest_api_utility.dart';
@@ -22,21 +23,40 @@ class TaskService {
     }
   }
 
-  /// Lists all tasks.
+  /// Fetches a single page of tasks.
   ///
-  /// [currentPage] and [pageSize] are optional pagination parameters.
-  ///
-  Future<TaskResponse> listAllTasks(
+  /// [currentPage] and [pageSize] are pagination parameters.
+  Future<TaskResponse> fetchTasksPage(
       {int currentPage = 1, int pageSize = 10}) async {
     try {
       final response = await api
           .get('agent/tasks?current_page=$currentPage&page_size=$pageSize');
       return TaskResponse.fromJson(response);
     } catch (e) {
-      throw Exception('Failed to list all tasks: $e');
+      throw Exception('Failed to fetch a page of tasks: $e');
     }
   }
 
+  /// Fetches all tasks across all pages.
+  // TODO: Temporaily make page size 10000 until pagination is fixed
+  Future<List<Task>> fetchAllTasks({int pageSize = 10000}) async {
+    int currentPage = 1;
+    List<Task> allTasks = [];
+
+    while (true) {
+      final response =
+          await fetchTasksPage(currentPage: currentPage, pageSize: pageSize);
+      allTasks.addAll(response.tasks);
+
+      if (response.tasks.length < pageSize) {
+        // No more tasks to fetch
+        break;
+      }
+      currentPage++;
+    }
+    return allTasks;
+  }
+
   /// Gets details about a specific task.
   ///
   /// [taskId] is the ID of the task.

frontend/lib/viewmodels/task_viewmodel.dart

@@ -52,8 +52,7 @@ class TaskViewModel with ChangeNotifier {
   /// Fetches tasks from the data source.
   Future<void> fetchTasks() async {
     try {
-      final TaskResponse tasksResponse = await _taskService.listAllTasks();
-      final tasksFromApi = tasksResponse.tasks;
+      final tasksFromApi = await _taskService.fetchAllTasks();
       _tasks = tasksFromApi
           .where((task) => !_taskService.isTaskDeleted(task.id))
           .toList();