Unable to accept Provider invitation if the invitee needs to use SSO for login

### Steps To Reproduce

1. Invite an account, that is a member of an organization with SSO enabled and enforced, as Service User/Admin
2. Accept the invitation by logging in via SSO

### Expected Result

Invitation is accepted

### Actual Result

Invitation is not accepted

### Screenshots or Videos

_No response_

### Additional Context

_No response_

### Build Version

2026.8.1

### Environment

Cloud (bitwarden.com)

### Environment Details

_No response_

### Issue Tracking Info

- [x] I understand that work is tracked outside of Github. A PR will be linked to this issue should one be opened to address it, but Bitwarden doesn't use fields like "assigned", "milestone", or "project" to track progress.

No files or tests are named. Start by reproducing the provider invitation acceptance flow for an organization member with enforced SSO, then trace the SSO login and invitation-handling entry points. Done means the invitation is accepted after the invitee logs in through SSO, matching the expected result.

Written by the indexing model from the issue text.