feat(core): add shared auth models for encrypted login

NEW/src/JdeScoping.Core/Models/Auth/LoginResultModel.cs

@@ -0,0 +1,14 @@
+using JdeScoping.Core.Models;
+
+namespace JdeScoping.Core.Models.Auth;
+
+/// <summary>
+/// Result returned from login API endpoint.
+/// </summary>
+/// <param name="Success">Whether authentication succeeded</param>
+/// <param name="ErrorMessage">Error message if failed</param>
+/// <param name="User">User info if successful</param>
+public record LoginResultModel(
+    bool Success,
+    string? ErrorMessage,
+    UserInfo? User);