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/userproduct/handler.go

@@ -0,0 +1,147 @@
+package userproduct
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"log/slog"
+	"net/http"
+
+	"github.com/food-ai/backend/internal/infra/middleware"
+	"github.com/go-chi/chi/v5"
+)
+
+// UserProductRepository is the data layer interface used by Handler.
+type UserProductRepository interface {
+	List(ctx context.Context, userID string) ([]*UserProduct, error)
+	Create(ctx context.Context, userID string, req CreateRequest) (*UserProduct, error)
+	BatchCreate(ctx context.Context, userID string, items []CreateRequest) ([]*UserProduct, error)
+	Update(ctx context.Context, id, userID string, req UpdateRequest) (*UserProduct, error)
+	Delete(ctx context.Context, id, userID string) error
+}
+
+// Handler handles /user-products HTTP requests.
+type Handler struct {
+	repo UserProductRepository
+}
+
+// NewHandler creates a new Handler.
+func NewHandler(repo UserProductRepository) *Handler {
+	return &Handler{repo: repo}
+}
+
+// List handles GET /user-products.
+func (handler *Handler) List(responseWriter http.ResponseWriter, request *http.Request) {
+	userID := middleware.UserIDFromCtx(request.Context())
+	userProducts, listError := handler.repo.List(request.Context(), userID)
+	if listError != nil {
+		slog.Error("list user products", "user_id", userID, "err", listError)
+		writeErrorJSON(responseWriter, http.StatusInternalServerError, "failed to list user products")
+		return
+	}
+	if userProducts == nil {
+		userProducts = []*UserProduct{}
+	}
+	writeJSON(responseWriter, http.StatusOK, userProducts)
+}
+
+// Create handles POST /user-products.
+func (handler *Handler) Create(responseWriter http.ResponseWriter, request *http.Request) {
+	userID := middleware.UserIDFromCtx(request.Context())
+	var req CreateRequest
+	if decodeError := json.NewDecoder(request.Body).Decode(&req); decodeError != nil {
+		writeErrorJSON(responseWriter, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	if req.Name == "" {
+		writeErrorJSON(responseWriter, http.StatusBadRequest, "name is required")
+		return
+	}
+
+	userProduct, createError := handler.repo.Create(request.Context(), userID, req)
+	if createError != nil {
+		slog.Error("create user product", "user_id", userID, "err", createError)
+		writeErrorJSON(responseWriter, http.StatusInternalServerError, "failed to create user product")
+		return
+	}
+	writeJSON(responseWriter, http.StatusCreated, userProduct)
+}
+
+// BatchCreate handles POST /user-products/batch.
+func (handler *Handler) BatchCreate(responseWriter http.ResponseWriter, request *http.Request) {
+	userID := middleware.UserIDFromCtx(request.Context())
+	var items []CreateRequest
+	if decodeError := json.NewDecoder(request.Body).Decode(&items); decodeError != nil {
+		writeErrorJSON(responseWriter, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	if len(items) == 0 {
+		writeJSON(responseWriter, http.StatusCreated, []*UserProduct{})
+		return
+	}
+
+	userProducts, batchError := handler.repo.BatchCreate(request.Context(), userID, items)
+	if batchError != nil {
+		slog.Error("batch create user products", "user_id", userID, "err", batchError)
+		writeErrorJSON(responseWriter, http.StatusInternalServerError, "failed to create user products")
+		return
+	}
+	writeJSON(responseWriter, http.StatusCreated, userProducts)
+}
+
+// Update handles PUT /user-products/{id}.
+func (handler *Handler) Update(responseWriter http.ResponseWriter, request *http.Request) {
+	userID := middleware.UserIDFromCtx(request.Context())
+	id := chi.URLParam(request, "id")
+
+	var req UpdateRequest
+	if decodeError := json.NewDecoder(request.Body).Decode(&req); decodeError != nil {
+		writeErrorJSON(responseWriter, http.StatusBadRequest, "invalid request body")
+		return
+	}
+
+	userProduct, updateError := handler.repo.Update(request.Context(), id, userID, req)
+	if errors.Is(updateError, ErrNotFound) {
+		writeErrorJSON(responseWriter, http.StatusNotFound, "user product not found")
+		return
+	}
+	if updateError != nil {
+		slog.Error("update user product", "id", id, "err", updateError)
+		writeErrorJSON(responseWriter, http.StatusInternalServerError, "failed to update user product")
+		return
+	}
+	writeJSON(responseWriter, http.StatusOK, userProduct)
+}
+
+// Delete handles DELETE /user-products/{id}.
+func (handler *Handler) Delete(responseWriter http.ResponseWriter, request *http.Request) {
+	userID := middleware.UserIDFromCtx(request.Context())
+	id := chi.URLParam(request, "id")
+
+	if deleteError := handler.repo.Delete(request.Context(), id, userID); deleteError != nil {
+		if errors.Is(deleteError, ErrNotFound) {
+			writeErrorJSON(responseWriter, http.StatusNotFound, "user product not found")
+			return
+		}
+		slog.Error("delete user product", "id", id, "err", deleteError)
+		writeErrorJSON(responseWriter, http.StatusInternalServerError, "failed to delete user product")
+		return
+	}
+	responseWriter.WriteHeader(http.StatusNoContent)
+}
+
+type errorResponse struct {
+	Error string `json:"error"`
+}
+
+func writeErrorJSON(responseWriter http.ResponseWriter, status int, msg string) {
+	responseWriter.Header().Set("Content-Type", "application/json")
+	responseWriter.WriteHeader(status)
+	_ = json.NewEncoder(responseWriter).Encode(errorResponse{Error: msg})
+}
+
+func writeJSON(responseWriter http.ResponseWriter, status int, value any) {
+	responseWriter.Header().Set("Content-Type", "application/json")
+	responseWriter.WriteHeader(status)
+	_ = json.NewEncoder(responseWriter).Encode(value)
+}