1. Auto dark mode: detect system prefers-color-scheme, auto-switch industrial/modern theme
2. Email quotation endpoint: POST /quotations/:id/email sends HTML email via SMTP
3. Camera barcode scanner: BarcodeDetector API with getUserMedia overlay in catalog
4. Returns with warranty: POST /returns endpoint with stock restoration and sale status tracking
5. Partial offline catalog: cache top 500 parts in IndexedDB, search when offline
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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>
