Tests the full transfer cycle against a real database: debit/credit,
transaction records, insufficient funds rejection, self-transfer
rejection, non-positive amounts, and sequential transfers.
Uses *.integration.test.ts convention — excluded from default test
runs, included with --integration flag in CI.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Covers the critical financial transfer path against a real database,
catching schema mismatches, constraint violations, and transaction
atomicity bugs that mocked unit tests cannot detect.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
