When add_account reported the Open already existed, the endpoint raised
409 before the DB-mirror step — so an account present in the ledger but
missing from libra's DB (a prior sync failure with no cross-DB atomicity,
or an out-of-band open) was stranded: invisible to permissions with no
recovery path. Now 409 only when the account is already in the DB too;
otherwise sync it and return success. Adds a recovery test.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>