Add tax repo to withTransaction in region service

Editor assessment

The subject reports that the tax repository was added to withTransaction in the region service — a precise, if jargon-dense, description of a transactional wiring correction. Readers familiar with the codebase will understand; outsiders must infer why omitting the repository from the transaction mattered. Fix is plausible for a correctness issue, though no scope marks the region service. No body exists to supply the missing rationale, which is unfortunate because transaction-boundary bugs are exactly where motivation helps. The message states the what accurately but leaves the why entirely to the diff.