fix(auth): link SSO sign-in to existing same-email accounts #4866

Bugbot Review

Bugbot Analysis Progress (3m 17s elapsed)

✅ Gathered PR context (5s)
✅ Completed bug detection (3m 11s)
✅ Posted analysis results (1s)

Final Result: Bugbot completed review - no issues found! ✅

Request ID: serverGenReqId_eb170fac-fbc3-4e60-85ce-6630dd34ede6

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit b08e6cf. Configure here.}