Confirm Bank Account Ownership

Confirm a pending (statement-created, undeclared) account as ours.

Releases the account's held entries: the matcher runs over them and, per the company's autonomy policy, they are best-effort GL-settled. On a grandfathered account (needs_ownership_review) it only stamps ownership_reviewed_at — its entries were already matched/settled at import. Idempotent on declared and reviewed-confirmed accounts. Accountant/owner (ZCT-257): confirming releases the account's held entries to the matcher and, per the autonomy policy, to GL settlement — a booking act, not a preference.

The row is resolved here rather than only inside the service because the gate needs a company_id before anything runs; the scoped load keeps the same 404-missing / 403-out-of-scope split the sibling routes have.