Add comprehensive test coverage for the purchases module:
- purchases-flow.integration.test.ts: Tests complete flow including
RFQ to PO conversion, partial/complete receipts, supplier invoicing,
returns handling, and cost variance detection
- receipts.service.test.ts: Unit tests for receipt creation,
confirmation, quantity validation, quality control, lot tracking,
and warehouse location assignment
Tests cover 128 scenarios across the purchases module including
success cases, error handling, and edge cases.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>