feat: rename ingredients→products, products→user_products; add barcode/OFF import

- Rename catalog: ingredient/* → product/* (canonical_name, barcode, nutrition per 100g)
- Rename pantry: product/* → userproduct/* (user-owned items with expiry)
- Squash migrations into single 001_initial_schema.sql (clean-db baseline)
- product_categories: add English canonical name column; fix COALESCE in queries
- Remove product_translations: product names are stored in their original language
- Add default_unit_name to product API responses via unit_translations JOIN
- Add cmd/importoff: bulk import from OpenFoodFacts JSONL dump (COPY + ON CONFLICT)
- Diary: support product_id entries alongside dish_id (CHECK num_nonnulls = 1)
- Home: getLoggedCalories joins both recipes and catalog products
- Flutter: rename models/providers/services to match backend rename
- Flutter: add barcode scan flow for diary (mobile_scanner, product_portion_sheet)
- Flutter: localise 6 new keys across 12 languages (barcode scan, portion weight)
- Routes: GET /products/search, GET /products/barcode/{barcode}, /user-products

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/domain/product/entity.go

@@ -1,41 +1,29 @@
 package product
 
-import "time"
+import (
+	"encoding/json"
+	"time"
+)
 
-// Product is a user's food item in their pantry.
+// Product is a catalog entry representing a food ingredient or packaged product.
+// CanonicalName holds the English name; localized names are resolved at query time.
 type Product struct {
-	ID                 string    `json:"id"`
-	UserID             string    `json:"user_id"`
-	PrimaryIngredientID *string  `json:"primary_ingredient_id"`
-	Name               string    `json:"name"`
-	Quantity           float64   `json:"quantity"`
-	Unit               string    `json:"unit"`
-	Category           *string   `json:"category"`
-	StorageDays        int       `json:"storage_days"`
-	AddedAt            time.Time `json:"added_at"`
-	ExpiresAt          time.Time `json:"expires_at"`
-	DaysLeft           int       `json:"days_left"`
-	ExpiringSoon       bool      `json:"expiring_soon"`
-}
+	ID            string          `json:"id"`
+	CanonicalName string          `json:"canonical_name"`
+	Aliases       json.RawMessage `json:"aliases"`       // []string, populated by read queries
+	Category      *string         `json:"category"`
+	CategoryName  *string         `json:"category_name"` // localized category display name
+	DefaultUnit     *string         `json:"default_unit"`
+	DefaultUnitName *string         `json:"default_unit_name,omitempty"`
+	Barcode       *string         `json:"barcode,omitempty"`
 
-// CreateRequest is the body for POST /products.
-type CreateRequest struct {
-	PrimaryIngredientID *string  `json:"primary_ingredient_id"`
-	// Accept both "primary_ingredient_id" (new) and "mapping_id" (legacy client) fields.
-	MappingID           *string  `json:"mapping_id"`
-	Name                string   `json:"name"`
-	Quantity            float64  `json:"quantity"`
-	Unit                string   `json:"unit"`
-	Category            *string  `json:"category"`
-	StorageDays         int      `json:"storage_days"`
-}
+	CaloriesPer100g *float64 `json:"calories_per_100g"`
+	ProteinPer100g  *float64 `json:"protein_per_100g"`
+	FatPer100g      *float64 `json:"fat_per_100g"`
+	CarbsPer100g    *float64 `json:"carbs_per_100g"`
+	FiberPer100g    *float64 `json:"fiber_per_100g"`
 
-// UpdateRequest is the body for PUT /products/{id}.
-// All fields are optional (nil = keep existing value).
-type UpdateRequest struct {
-	Name        *string  `json:"name"`
-	Quantity    *float64 `json:"quantity"`
-	Unit        *string  `json:"unit"`
-	Category    *string  `json:"category"`
-	StorageDays *int     `json:"storage_days"`
+	StorageDays *int      `json:"storage_days"`
+	CreatedAt   time.Time `json:"created_at"`
+	UpdatedAt   time.Time `json:"updated_at"`
 }