LG-13739: Avoid sending new device email after account creation

[aduth]

🎫 Ticket

LG-13739

🛠 Summary of changes

Updates logic of User#authenticated_device? to consider the device authenticated if it was the one that had created the account. This fixes an issue where the new-device email would be unexpectedly sent the first time the user signs in after creating an account, even if that was the device they'd used to create the account.

The issue stems from the fact that we previously relied on :sign_in_after_2fa event existing for the device, but this event is only created if a user authenticates with 2FA, which doesn't happen during the account creation process.

📜 Testing Plan

1. In a private browsing window, go to http://localhost:3000
2. Create an account
3. Once you reach the account dashboard, sign out
4. Sign in to that new account

Before: You'd receive a new device sign-in email
After: You don't receive a new device sign-in email