update api

lib/core/errors/failures.dart

@@ -39,3 +39,23 @@ class NotFoundFailure extends Failure {
 class UnauthorizedFailure extends Failure {
   const UnauthorizedFailure([super.message = 'Unauthorized access']);
 }
+
+/// Authentication failure
+class AuthenticationFailure extends Failure {
+  const AuthenticationFailure([super.message = 'Authentication failed']);
+}
+
+/// Invalid credentials failure
+class InvalidCredentialsFailure extends Failure {
+  const InvalidCredentialsFailure([super.message = 'Invalid email or password']);
+}
+
+/// Token expired failure
+class TokenExpiredFailure extends Failure {
+  const TokenExpiredFailure([super.message = 'Token has expired']);
+}
+
+/// Conflict failure (e.g., email already exists)
+class ConflictFailure extends Failure {
+  const ConflictFailure([super.message = 'Resource already exists']);
+}