[Bug]: New account sync using GoCardless causes issue

### What happened?

I was trying to create a new budget with sync using GoCardless (created before 2025), and account authorization workflow shows success until GoCardless handsover token to Actual.
Actual budget seems to have issue with the gocardless authorization token and just shows a popup saying account created failed due to GoCardless error.
I have earlier used gocardless account sync on multiple accounts and it always worked, gocardless still shows success in the workflow, but somehow Actual fails to recognize the token as valid ?
My Actual server & client versions are up to date : v26.9.0

### How can we reproduce the issue?

Add account
Choose GoCardless Sync
Authorize in account after giving details in gocardless popup
Look at success in gocardless popup
come back to actual and see error screen

### Where are you hosting Actual?

NAS

### What browsers are you seeing the problem on?

Chrome

### Operating System

Windows 11

The issue points to the GoCardless sync authorization handoff in the new-account flow. Reproduce it once and capture logs at the point the popup returns to Actual with the token. No specific files or tests are listed, so first inspect the GoCardless provider/auth callback and token validation path in the sync integration code, then run any account-sync test or integration suite if present. Completion is clear when a newly connected GoCardless account succeeds without the post-auth popup error.

Scritto dal modello di indicizzazione a partire dal testo della issue.