refactor(apps): simplify API layer by removing redundant wrapper classes

- Remove ApiClientWrapper and MockApiClientWrapper
- Simplify IApiClient interface
- Update dependency injection configuration
- Optimize calendar service and AG-UI chat models

apps/lib/core/api/api_client.dart

@@ -1,9 +1,10 @@
 import 'package:dio/dio.dart';
 import 'api_exception.dart';
 import 'api_interceptor.dart';
+import 'i_api_client.dart';
 import '../storage/token_storage.dart';
 
-class ApiClient {
+class ApiClient implements IApiClient {
   final Dio _dio;
   final TokenStorage _tokenStorage;
   final ApiInterceptor _interceptor;
@@ -44,6 +45,7 @@ class ApiClient {
     };
   }
 
+  @override
   Future<Response<T>> get<T>(String path, {Options? options}) async {
     try {
       return await _dio.get<T>(path, options: options);
@@ -52,6 +54,7 @@ class ApiClient {
     }
   }
 
+  @override
   Future<Response<T>> post<T>(
     String path, {
     dynamic data,
@@ -64,6 +67,7 @@ class ApiClient {
     }
   }
 
+  @override
   Future<Response<T>> patch<T>(
     String path, {
     dynamic data,
@@ -76,6 +80,7 @@ class ApiClient {
     }
   }
 
+  @override
   Future<Response<T>> delete<T>(
     String path, {
     dynamic data,