feat(F-193): completed feature

work/artifacts/F-193/implementer.md

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+# 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 |