Set EndpointAuthType enum underlying type to byte

Explicitly define EndpointAuthType as a byte-based enum for improved memory efficiency and better interoperability with systems requiring a specific underlying type.

src/ReC.Domain/Constants/EndpointAuthType.cs

@@ -1,6 +1,6 @@
 namespace ReC.Domain.Constants;
 
-public enum EndpointAuthType
+public enum EndpointAuthType : byte
 {
     NoAuth = 0,
     ApiKey = 1,