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>

client/lib/features/diary/barcode_scan_screen.dart

@@ -0,0 +1,107 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:mobile_scanner/mobile_scanner.dart';
+
+import '../../core/auth/auth_provider.dart';
+import '../../l10n/app_localizations.dart';
+import '../../shared/models/product.dart';
+import 'food_product_service.dart';
+import 'product_portion_sheet.dart';
+
+/// Screen that activates the device camera to scan a barcode.
+/// On successful scan it looks up the catalog product and shows
+/// [ProductPortionSheet] to confirm the portion before adding to diary.
+class BarcodeScanScreen extends ConsumerStatefulWidget {
+  const BarcodeScanScreen({
+    super.key,
+    required this.mealType,
+    required this.date,
+    required this.onAdded,
+  });
+
+  final String mealType;
+  final String date;
+  final VoidCallback onAdded;
+
+  @override
+  ConsumerState<BarcodeScanScreen> createState() => _BarcodeScanScreenState();
+}
+
+class _BarcodeScanScreenState extends ConsumerState<BarcodeScanScreen> {
+  bool _scanning = true;
+
+  void _onBarcodeDetected(BarcodeCapture capture) async {
+    if (!_scanning) return;
+    final rawValue = capture.barcodes.firstOrNull?.rawValue;
+    if (rawValue == null) return;
+
+    setState(() => _scanning = false);
+
+    final l10n = AppLocalizations.of(context)!;
+    final service = FoodProductService(ref.read(apiClientProvider));
+    final catalogProduct = await service.getByBarcode(rawValue);
+
+    if (!mounted) return;
+
+    if (catalogProduct == null) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text(l10n.productNotFound)),
+      );
+      setState(() => _scanning = true);
+      return;
+    }
+
+    _showPortionSheet(catalogProduct);
+  }
+
+  void _showPortionSheet(CatalogProduct catalogProduct) {
+    showModalBottomSheet(
+      context: context,
+      isScrollControlled: true,
+      builder: (_) => ProductPortionSheet(
+        catalogProduct: catalogProduct,
+        onConfirm: (portionGrams) => _addToDiary(catalogProduct, portionGrams),
+      ),
+    ).then((_) {
+      if (mounted) setState(() => _scanning = true);
+    });
+  }
+
+  Future<void> _addToDiary(
+      CatalogProduct catalogProduct, double portionGrams) async {
+    final l10n = AppLocalizations.of(context)!;
+    try {
+      await ref.read(apiClientProvider).post('/diary', data: {
+        'product_id': catalogProduct.id,
+        'portion_g': portionGrams,
+        'meal_type': widget.mealType,
+        'date': widget.date,
+        'source': 'barcode',
+      });
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text(catalogProduct.displayName)),
+        );
+        widget.onAdded();
+        Navigator.pop(context);
+      }
+    } catch (_) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text(l10n.addFailed)),
+        );
+      }
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context)!;
+    return Scaffold(
+      appBar: AppBar(title: Text(l10n.scanBarcode)),
+      body: MobileScanner(
+        onDetect: _onBarcodeDetected,
+      ),
+    );
+  }
+}