added auth with a simple UI

api/OED.Api/Infrastructure/Auth/TokenEcryptor.cs

@@ -0,0 +1,18 @@
+using Microsoft.AspNetCore.DataProtection;
+
+namespace OED.Api.Infrastructure.Auth;
+
+public interface ITokenEncryptor
+{
+    string Encrypt(string plaintext);
+    string Decrypt(string ciphertext);
+}
+
+// Uses ASP.NET Data Protection — handles key management, rotation, and storage automatically
+public class TokenEncryptor(IDataProtectionProvider provider) : ITokenEncryptor
+{
+    private readonly IDataProtector _protector = provider.CreateProtector("Eve.RefreshToken.v1");
+
+    public string Encrypt(string plaintext) => _protector.Protect(plaintext);
+    public string Decrypt(string ciphertext) => _protector.Unprotect(ciphertext);
+}