feat: add generate refresh token

Security/Services/AuthService.cs

@@ -5,4 +5,7 @@ namespace Mirea.Api.Security.Services;
 public class AuthService()
 {
     public TimeSpan Lifetime { private get; init; }
+
+    private static string GenerateRefreshToken() => Guid.NewGuid().ToString().Replace("-", "") +
+                                                    GeneratorKey.GenerateString(32);
 }