Quotation and layaway endpoints were calling calculate_totals() on raw input items without looking up unit_price/tax_rate from inventory, causing KeyError. Added _enrich_items() helper (with customer price tier support). Also removed non-existent discount_total column from quotations INSERT, and made layaway complete accept a final payment for the remaining balance. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>