db/db.go: TxFromContext/ContextWithTx for transaction propagation,
Querier interface (QueryRow/Query/Exec), ScanRow generic helper,
ClampLimit/ClampOffset pagination guards.
db/postgres/postgres.go: NewPool with ping validation, Transactor
backed by pgxpool (BeginTx → fn → commit/rollback), connOrTx helper
that returns the active transaction from context or falls back to pool.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Masahiko AMANO
2c83073903