Specify byte as underlying type for ResultType enum

Changed ResultType enum declaration to explicitly use byte as its underlying type for improved memory efficiency and clarity.

src/ReC.Domain/Constants/ResultType.cs

@@ -1,6 +1,6 @@
 namespace ReC.Domain.Constants;
 
-public enum ResultType
+public enum ResultType : byte
 {
     Pre = 1,
     Main,