fix: include <concepts> in arithmetic_traits.hpp for concept definitions

CHANGELOG.md

@@ -6,6 +6,10 @@ All notable changes to this project will be documented in this file.
 
 - Update test/CMakeLists.txt to implicitly take care of including the Catch2 submodule
 
+### Type Traits
+
+- Fix missing concept header in `arithmetic_traits.hpp`
+
 <!-- insertion marker -->
 ## [0.1.0](https://github.com/repo/owner/releases/tag/0.1.0) - 2026-02-27
 

include/mstd/type_traits/math/arithmetic_traits.hpp

@@ -23,6 +23,8 @@
 #ifndef __MSTD__TYPE_TRAITS__MATH__ARITHMETIC_TRAITS_HPP__
 #define __MSTD__TYPE_TRAITS__MATH__ARITHMETIC_TRAITS_HPP__
 
+#include <concepts>
+
 namespace mstd
 {
     /**