Refactor: Remove GlobalVar and replace with IAppSettings; restructure affected infrastructure, services, and view models for dependency injection.

Jugenddienst Stunden/Interfaces/IApiClient.cs

@@ -1,5 +1,8 @@
 namespace Jugenddienst_Stunden.Interfaces;
 
+/// <summary>
+/// Defines methods for making HTTP requests to a specified API.
+/// </summary>
 internal interface IApiClient {
 	Task<T> GetAsync<T>(string path, IDictionary<string, string?>? query = null, CancellationToken ct = default);