# F-193 — Implementer Evidence

## Feature
Show product expiry and shipping weight on storefront + authoritative variant weight in shipping.

## Changes

### 1. `project/migrations/057_product_variant_weight_and_expiry.js` (new)

Adds `weight_grams` column to `catalog_product_variants`:
- `integer`, nullable, no default
- CHECK: `weight_grams IS NULL OR weight_grams > 0`
- After `ean` column

### 2. `project/src/modules/catalog/domain/variant.ts`

Added `weightGrams` to `ProductVariant`, `NewProductVariant`, and `ProductVariantPatch`.

### 3. `project/src/modules/catalog/infrastructure/pg-variant-repository.ts`

- Added `weight_grams` to `VariantRow` interface
- Added `['weightGrams', 'weight_grams']` to `UPDATABLE` array
- Updated `create()` to INSERT `weight_grams`
- Updated `toVariant()` to map `weight_grams → weightGrams`

### 4. `project/src/modules/catalog/api/catalog.routes.ts`

- Added `weightGrams` to `newVariantSchema` (zod, optional, integer >= 1)
- Added `weightGrams` to `serializeVariant()` output

### 5. `project/src/modules/checkout/application/checkout-service.ts`

- Extended `getCartWeightKg` parameter type to include `variantId`
- Updated call site to pass full `cart.items` (no mapping needed)

### 6. `project/src/modules/checkout/api/checkout.routes.ts`

- Rewrote `getCartWeightKg` to:
  - Fetch variant-level `weight_grams` from `catalog_product_variants`
  - Fetch product-level `unit_weight_kg` as fallback
  - Prefer variant weight (g → kg) when available
  - Fall back to product weight (kg) when variant weight is null

### 7. `project/frontend/src/lib/api.ts`

- Added `weightGrams: number | null` to `ProductVariant` interface

### 8. `project/frontend/src/types/api.ts`

- Added `expirationDate?: string` to `Product` interface

### 9. `project/frontend/src/app/products/[slug]/page.tsx`

Added expiry date and weight display in the price box:
- `Caduca: {date}` — when `product.expirationDate` is set
- `Peso: {X.Y kg}` or `Peso: {X g}` — from `primaryVariant.weightGrams`

### Existing (no changes needed)

- `catalog_products.expiration_date` — already exists from migration 038
- `catalog_products.unit_weight_kg` — already exists as fallback
- `ShippingService` — already takes `cartWeightKg` and filters by `maxWeightKg`
- `serializeProduct()` — already serializes `expirationDate`

## Verification

| Check | Result |
|-------|--------|
| `npx tsc --noEmit` (backend) | 0 errors |
| `npx tsc --noEmit` (frontend) | 0 errors |
| `npm test` (backend) | 269 passed, 96 skipped |
| `./scripts/verify.sh` | OK |