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/diary/entity.go

@@ -7,14 +7,15 @@ type Entry struct {
 	ID        string    `json:"id"`
 	Date      string    `json:"date"` // YYYY-MM-DD
 	MealType  string    `json:"meal_type"`
-	Name      string    `json:"name"`           // from dishes JOIN
+	Name      string    `json:"name"`                // from dishes or products JOIN
 	Portions  float64   `json:"portions"`
-	Calories  *float64  `json:"calories,omitempty"`  // recipe.calories_per_serving * portions
+	Calories  *float64  `json:"calories,omitempty"`  // recipe.calories_per_serving * portions, or product * portion_g
 	ProteinG  *float64  `json:"protein_g,omitempty"`
 	FatG      *float64  `json:"fat_g,omitempty"`
 	CarbsG    *float64  `json:"carbs_g,omitempty"`
 	Source    string    `json:"source"`
-	DishID    string    `json:"dish_id"`
+	DishID    *string   `json:"dish_id,omitempty"`
+	ProductID *string   `json:"product_id,omitempty"`
 	RecipeID  *string   `json:"recipe_id,omitempty"`
 	PortionG  *float64  `json:"portion_g,omitempty"`
 	JobID     *string   `json:"job_id,omitempty"`
@@ -23,13 +24,14 @@ type Entry struct {
 
 // CreateRequest is the body for POST /diary.
 type CreateRequest struct {
-	Date     string   `json:"date"`
-	MealType string   `json:"meal_type"`
-	Name     string   `json:"name"`     // input-only; used if DishID is nil
-	Portions float64  `json:"portions"`
-	Source   string   `json:"source"`
-	DishID   *string  `json:"dish_id"`
-	RecipeID *string  `json:"recipe_id"`
-	PortionG *float64 `json:"portion_g"`
-	JobID    *string  `json:"job_id"`
+	Date      string   `json:"date"`
+	MealType  string   `json:"meal_type"`
+	Name      string   `json:"name"`      // input-only; used if DishID is nil and ProductID is nil
+	Portions  float64  `json:"portions"`
+	Source    string   `json:"source"`
+	DishID    *string  `json:"dish_id"`
+	ProductID *string  `json:"product_id"`
+	RecipeID  *string  `json:"recipe_id"`
+	PortionG  *float64 `json:"portion_g"`
+	JobID     *string  `json:"job_id"`
 }