Account form validation is more reliable

The account-level user form got several state-management fixes that you will feel every time you edit your profile:

• Validation errors clear as you type. Previously an error message could persist on a field even after you had fixed the issue, until you tabbed away or saved.
• Submit states release. Submit-in-progress states no longer get stuck if the request fails mid-flight — the spinner unwinds, the form re-enables, the error surfaces clearly.
• Optimistic UI restores cleanly on failure. If a save fails for any reason, the form rolls back to the last good values instead of holding the in-flight changes in a weird half-state.

It is the same form it always was, but a lot less stressful to interact with.