fix: update fallback behavior to return empty responses when backend is unavailable

src/FrontOffice.Main/Utilities/ClubMembershipService.cs

@@ -35,12 +35,12 @@ public class ClubMembershipService
         }
         catch
         {
-            // Fallback to mock data if backend is unavailable
+            // Return empty membership if backend is unavailable
             return new ClubMembershipDto
             {
-                UserId = 1,
+                UserId = 0,
                 IsActive = false,
-                Status = "Inactive",
+                Status = string.Empty,
                 DaysRemaining = null
             };
         }