feat: disable user different account button for new users

[mihakrajnc]

Pull Request Description

This PR disables the "USE A DIFFERENT ACCOUNT" button on the authentication screen for new users.

Test Instructions

Prerequisites

• MetaForge installed

Test Steps

1. Create a new user with metaforge create - this sets up the auto-login token
2. Start explorer with metaforge explorer run 7774 --clear (--clear will delete all app data and caches)
3. Verify that the button is not there
4. Enter world
5. Exit Explorer
6. Start Explorer again - button should now be visible.

Additional Testing Notes

• Note any edge cases to verify
• Mention specific areas that need careful testing
• List known limitations or potential issues

Quality Checklist

• Changes have been tested locally
• Documentation has been updated (if required)
• Performance impact has been considered
• For SDK features: Test scene is included

Code Review Reference

Please review our Code Review Standards before submitting.

[github-actions]

Windows and Mac build successful in Unity Cloud! You can find a link to the downloadable artifact below.

Name	Link
Commit	b68b576
Logs	https://github.com/decentraland/unity-explorer/actions/runs/23497623054
Download Windows	https://github.com/decentraland/unity-explorer/suites/61811934725/artifacts/6084113696
Download Windows S3	https://explorer-artifacts.decentraland.org/@dcl/unity-explorer/branch/feat/disable_diff_acc_for_new_users/pr-20177-b68b576/Decentraland_windows64.zip
Download Mac	https://github.com/decentraland/unity-explorer/suites/61811934725/artifacts/6084297044
Download Mac S3	https://explorer-artifacts.decentraland.org/@dcl/unity-explorer/branch/feat/disable_diff_acc_for_new_users/pr-20177-b68b576/Decentraland_macos.zip
Built on	2026-03-24T16:08:30Z