fix(passport): add user-friendly message for 409 error in registerOffchain

Following the ts-immutable-sdk Passport v3 refactoring (commit 240cd2f15,
Dec 8 2025), which introduced stricter validation via toUserImx() during
user registration, we now explicitly handle the 409 Conflict error in
ImxRegisterScript.

When a user is already registered off-chain, the API returns a 409 error with
USER_REGISTRATION_ERROR type. This change detects this specific scenario and
displays a user-friendly message: 'Passport account already registered'.

This ensures the UI tests (test_4_imx_functions) continue to pass and provides
a better user experience when attempting to register an already registered
account.

Author: rodrigo-fournier-immutable

src/Packages/Passport/Samples~/SamplesScenesScripts/Scripts/Passport/ImxRegister/ImxRegisterScript.cs

@@ -43,7 +43,16 @@ public async void RegisterOffchain()
         }
         catch (PassportException e)
         {
-            ShowOutput($"Unable to register off-chain: {e.Message} ({e.Type})");
+            // Handle 409 - account already registered
+            if (e.Type == PassportErrorType.USER_REGISTRATION_ERROR &&
+                (e.Message.Contains("409") || e.Message.Contains("already registered")))
+            {
+                ShowOutput("Passport account already registered");
+            }
+            else
+            {
+                ShowOutput($"Unable to register off-chain: {e.Message} ({e.Type})");
+            }
         }
         catch (Exception e)
         {
@@ -58,4 +67,4 @@ private void ShowOutput(string message)
             Output.text = message;
         }
     }
-}
+}