Adds the primitives a host webhook needs to keep the ledger current in
real time, so the importer is a backstop rather than the only path:
- ledgerRowFromBalanceTransaction(): the canonical row builder (the
import command now delegates to it), with refund→charge buyer fallback.
- recordBalanceTransaction(): idempotent upsert on the txn_ id that never
downgrades a known customer_id/email to null (so a webhook's resolved
buyer isn't clobbered by a later importer pass that couldn't resolve it).
- syncLedgerForCharge(): retrieves a charge + its refunds and upserts their
balance transactions, user-independent, never throws (logs + returns 0).
Facade @methods + 3 LedgerMetricsTest cases (upsert idempotency, no-downgrade,
non-charge-id guard). Full suite 1461 green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>