after refactor cleanup

DiunaBI.UI.Shared/Services/IGoogleAuthService.cs

@@ -0,0 +1,13 @@
+namespace DiunaBI.UI.Shared.Services;
+
+/// <summary>
+/// Platform-agnostic interface for Google authentication
+/// </summary>
+public interface IGoogleAuthService
+{
+    /// <summary>
+    /// Initiate Google Sign-In flow
+    /// </summary>
+    /// <returns>True if authentication was initiated successfully</returns>
+    Task<bool> SignInAsync();
+}