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/features/chat/data/models/ag_ui_event.dart

@@ -89,7 +89,7 @@ final _typeToFactory = {
   AgUiEventType.unknown: UnknownAgUiEvent.fromJson,
 };
 
-@JsonSerializable()
+@JsonSerializable(createFactory: false)
 class AgUiEvent {
   final AgUiEventType type;
 
@@ -104,7 +104,7 @@ class AgUiEvent {
   Map<String, dynamic> toJson() => _$AgUiEventToJson(this);
 }
 
-@JsonSerializable()
+@JsonSerializable(createFactory: false, createToJson: false)
 class UnknownAgUiEvent extends AgUiEvent {
   final Map<String, dynamic> rawJson;