feat: Implement ApiService with Dio for standardized API requests and responses using ApiResponse entity.

apps/mobile/packages/domain/lib/krow_domain.dart

@@ -6,6 +6,9 @@
 /// Note: Repository Interfaces are now located in their respective Feature packages.
 library;
 
+// Core
+export 'src/entities/core/services/api_service/api_response.dart';
+
 // Users & Membership
 export 'src/entities/users/user.dart';
 export 'src/entities/users/staff.dart';

apps/mobile/packages/domain/lib/src/entities/core/services/api_service/api_response.dart

@@ -0,0 +1,22 @@
+/// Represents a standardized response from the API.
+class ApiResponse {
+  /// Creates an [ApiResponse].
+  const ApiResponse({
+    required this.code,
+    required this.message,
+    this.data,
+    this.errors = const <String, dynamic>{},
+  });
+
+  /// The response code (e.g., '200', '404', or custom error code).
+  final String code;
+
+  /// A descriptive message about the response.
+  final String message;
+
+  /// The payload returned by the API.
+  final dynamic data;
+
+  /// A map of field-specific error messages, if any.
+  final Map<String, dynamic?> errors;
+}