feat: Flutter client localisation (12 languages)

Add flutter_localizations + intl, 12 ARB files (en/ru/es/de/fr/it/pt/zh/ja/ko/ar/hi),
replace all hardcoded Russian UI strings with AppLocalizations, detect system locale
on first launch, localise bottom nav bar labels, document rule in CLAUDE.md.

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

client/lib/features/scan/dish_result_screen.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
+import 'package:food_ai/l10n/app_localizations.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../../core/storage/local_preferences_provider.dart';
@@ -17,6 +18,8 @@ class DishResultSheet extends ConsumerStatefulWidget {
     required this.onAdded,
     this.preselectedMealType,
     this.jobId,
+    this.targetDate,
+    this.createdAt,
   });
 
   final DishResult dish;
@@ -24,6 +27,13 @@ class DishResultSheet extends ConsumerStatefulWidget {
   final String? preselectedMealType;
   final String? jobId;
 
+  /// The diary date to add the entry to (YYYY-MM-DD).
+  /// Falls back to [createdAt] date, then today.
+  final String? targetDate;
+
+  /// Job creation timestamp used as fallback date when [targetDate] is null.
+  final DateTime? createdAt;
+
   @override
   ConsumerState<DishResultSheet> createState() => _DishResultSheetState();
 }
@@ -32,6 +42,7 @@ class _DishResultSheetState extends ConsumerState<DishResultSheet> {
   late int _selectedIndex;
   late int _portionGrams;
   late String _mealType;
+  late DateTime _selectedDiaryDate;
   bool _saving = false;
 
   final TextEditingController _portionController = TextEditingController();
@@ -43,9 +54,19 @@ class _DishResultSheetState extends ConsumerState<DishResultSheet> {
     _portionGrams = widget.dish.candidates.isNotEmpty
         ? widget.dish.candidates.first.weightGrams
         : 300;
-    _mealType = widget.preselectedMealType ??
-        kAllMealTypes.first.id;
+    _mealType = widget.preselectedMealType ?? kAllMealTypes.first.id;
     _portionController.text = '$_portionGrams';
+    if (widget.targetDate != null) {
+      final parts = widget.targetDate!.split('-');
+      _selectedDiaryDate = DateTime(
+        int.parse(parts[0]), int.parse(parts[1]), int.parse(parts[2]),
+      );
+    } else if (widget.createdAt != null) {
+      final createdAtDate = widget.createdAt!;
+      _selectedDiaryDate = DateTime(createdAtDate.year, createdAtDate.month, createdAtDate.day);
+    } else {
+      _selectedDiaryDate = DateTime.now();
+    }
   }
 
   @override
@@ -79,6 +100,17 @@ class _DishResultSheetState extends ConsumerState<DishResultSheet> {
     });
   }
 
+  Future<void> _pickDate() async {
+    final now = DateTime.now();
+    final pickedDate = await showDatePicker(
+      context: context,
+      initialDate: _selectedDiaryDate,
+      firstDate: now.subtract(const Duration(days: 365)),
+      lastDate: now,
+    );
+    if (pickedDate != null) setState(() => _selectedDiaryDate = pickedDate);
+  }
+
   void _onPortionEdited(String value) {
     final parsed = int.tryParse(value);
     if (parsed != null && parsed >= 10) {
@@ -90,8 +122,8 @@ class _DishResultSheetState extends ConsumerState<DishResultSheet> {
     if (_saving) return;
     setState(() => _saving = true);
 
-    final selectedDate = ref.read(selectedDateProvider);
-    final dateString = formatDateForDiary(selectedDate);
+    final l10n = AppLocalizations.of(context)!;
+    final dateString = formatDateForDiary(_selectedDiaryDate);
 
     final scaledCalories = _scale(_selected.calories);
     final scaledProtein  = _scale(_selected.proteinG);
@@ -120,7 +152,7 @@ class _DishResultSheetState extends ConsumerState<DishResultSheet> {
       if (mounted) {
         setState(() => _saving = false);
         ScaffoldMessenger.of(context).showSnackBar(
-          const SnackBar(content: Text('Не удалось добавить. Попробуйте ещё раз.')),
+          SnackBar(content: Text(l10n.addFailed)),
         );
       }
     }
@@ -128,6 +160,7 @@ class _DishResultSheetState extends ConsumerState<DishResultSheet> {
 
   @override
   Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context)!;
     final theme = Theme.of(context);
     final hasCandidates = widget.dish.candidates.isNotEmpty;
 
@@ -150,7 +183,7 @@ class _DishResultSheetState extends ConsumerState<DishResultSheet> {
           padding: const EdgeInsets.fromLTRB(20, 0, 8, 0),
           child: Row(
             children: [
-              Text('Распознано блюдо', style: theme.textTheme.titleMedium),
+              Text(l10n.dishResultTitle, style: theme.textTheme.titleMedium),
               const Spacer(),
               IconButton(
                 icon: const Icon(Icons.close),
@@ -179,7 +212,7 @@ class _DishResultSheetState extends ConsumerState<DishResultSheet> {
                     ),
                     const SizedBox(height: 8),
                     Text(
-                      'КБЖУ приблизительные — определены по фото.',
+                      l10n.nutritionApproximate,
                       style: theme.textTheme.bodySmall?.copyWith(
                         color: theme.colorScheme.onSurfaceVariant,
                       ),
@@ -199,6 +232,11 @@ class _DishResultSheetState extends ConsumerState<DishResultSheet> {
                         if (value != null) setState(() => _mealType = value);
                       },
                     ),
+                    const SizedBox(height: 20),
+                    _DatePickerRow(
+                      date: _selectedDiaryDate,
+                      onTap: _pickDate,
+                    ),
                     const SizedBox(height: 16),
                   ],
                 )
@@ -207,13 +245,13 @@ class _DishResultSheetState extends ConsumerState<DishResultSheet> {
                     mainAxisSize: MainAxisSize.min,
                     children: [
                       Text(
-                        'Блюдо не распознано',
+                        l10n.dishNotRecognized,
                         style: theme.textTheme.titleMedium,
                       ),
                       const SizedBox(height: 8),
                       FilledButton(
                         onPressed: () => Navigator.pop(context),
-                        child: const Text('Попробовать снова'),
+                        child: Text(l10n.tryAgain),
                       ),
                     ],
                   ),
@@ -232,7 +270,7 @@ class _DishResultSheetState extends ConsumerState<DishResultSheet> {
                         width: 20,
                         child: CircularProgressIndicator(strokeWidth: 2),
                       )
-                    : const Text('Добавить в журнал'),
+                    : Text(l10n.addToJournal),
               ),
             ),
           ),
@@ -241,6 +279,47 @@ class _DishResultSheetState extends ConsumerState<DishResultSheet> {
   }
 }
 
+// ---------------------------------------------------------------------------
+// Date picker row
+// ---------------------------------------------------------------------------
+
+class _DatePickerRow extends StatelessWidget {
+  final DateTime date;
+  final VoidCallback onTap;
+
+  const _DatePickerRow({required this.date, required this.onTap});
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context)!;
+    final now = DateTime.now();
+    final today = DateTime(now.year, now.month, now.day);
+    final target = DateTime(date.year, date.month, date.day);
+
+    final String label;
+    if (target == today) {
+      label = l10n.today;
+    } else if (target == today.subtract(const Duration(days: 1))) {
+      label = l10n.yesterday;
+    } else {
+      label = '${date.day.toString().padLeft(2, '0')}.${date.month.toString().padLeft(2, '0')}.${date.year}';
+    }
+
+    return InkWell(
+      onTap: onTap,
+      borderRadius: BorderRadius.circular(12),
+      child: InputDecorator(
+        decoration: InputDecoration(
+          labelText: l10n.dateLabel,
+          border: const OutlineInputBorder(),
+          suffixIcon: const Icon(Icons.calendar_today_outlined),
+        ),
+        child: Text(label),
+      ),
+    );
+  }
+}
+
 // ---------------------------------------------------------------------------
 // Candidates selector
 // ---------------------------------------------------------------------------
@@ -258,11 +337,12 @@ class _CandidatesSection extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context)!;
     final theme = Theme.of(context);
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
-        Text('Выберите блюдо', style: theme.textTheme.titleMedium),
+        Text(l10n.selectDish, style: theme.textTheme.titleMedium),
         const SizedBox(height: 8),
         ...candidates.asMap().entries.map((entry) {
           final index = entry.key;
@@ -378,6 +458,7 @@ class _NutritionCard extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context)!;
     final theme = Theme.of(context);
     return Card(
       child: Padding(
@@ -388,7 +469,7 @@ class _NutritionCard extends StatelessWidget {
             Row(
               children: [
                 Text(
-                  '≈ ${calories.toInt()} ккал',
+                  '≈ ${calories.toInt()} ${l10n.caloriesUnit}',
                   style: theme.textTheme.titleLarge?.copyWith(
                     fontWeight: FontWeight.bold,
                     color: theme.colorScheme.primary,
@@ -396,7 +477,7 @@ class _NutritionCard extends StatelessWidget {
                 ),
                 const Spacer(),
                 Tooltip(
-                  message: 'Приблизительные значения на основе фото',
+                  message: l10n.nutritionApproximate,
                   child: Text(
                     '≈',
                     style: theme.textTheme.titleLarge?.copyWith(
@@ -411,18 +492,18 @@ class _NutritionCard extends StatelessWidget {
               mainAxisAlignment: MainAxisAlignment.spaceBetween,
               children: [
                 _MacroChip(
-                  label: 'Белки',
-                  value: '${proteinG.toStringAsFixed(1)} г',
+                  label: l10n.proteinLabel,
+                  value: '${proteinG.toStringAsFixed(1)} ${l10n.gramsUnit}',
                   color: Colors.blue,
                 ),
                 _MacroChip(
-                  label: 'Жиры',
-                  value: '${fatG.toStringAsFixed(1)} г',
+                  label: l10n.fatLabel,
+                  value: '${fatG.toStringAsFixed(1)} ${l10n.gramsUnit}',
                   color: Colors.orange,
                 ),
                 _MacroChip(
-                  label: 'Углеводы',
-                  value: '${carbsG.toStringAsFixed(1)} г',
+                  label: l10n.carbsLabel,
+                  value: '${carbsG.toStringAsFixed(1)} ${l10n.gramsUnit}',
                   color: Colors.green,
                 ),
               ],
@@ -482,11 +563,12 @@ class _PortionRow extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context)!;
     final theme = Theme.of(context);
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
-        Text('Порция', style: theme.textTheme.titleSmall),
+        Text(l10n.portion, style: theme.textTheme.titleSmall),
         const SizedBox(height: 8),
         Row(
           children: [
@@ -502,9 +584,9 @@ class _PortionRow extends StatelessWidget {
                 keyboardType: TextInputType.number,
                 inputFormatters: [FilteringTextInputFormatter.digitsOnly],
                 onChanged: onChanged,
-                decoration: const InputDecoration(
-                  suffixText: 'г',
-                  border: OutlineInputBorder(),
+                decoration: InputDecoration(
+                  suffixText: l10n.gramsUnit,
+                  border: const OutlineInputBorder(),
                 ),
               ),
             ),
@@ -535,11 +617,12 @@ class _MealTypeDropdown extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context)!;
     final theme = Theme.of(context);
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
-        Text('Приём пищи', style: theme.textTheme.titleSmall),
+        Text(l10n.mealType, style: theme.textTheme.titleSmall),
         const SizedBox(height: 8),
         DropdownButtonFormField<String>(
           initialValue: selected,
@@ -550,7 +633,7 @@ class _MealTypeDropdown extends StatelessWidget {
               .map((mealTypeOption) => DropdownMenuItem(
                     value: mealTypeOption.id,
                     child: Text(
-                        '${mealTypeOption.emoji} ${mealTypeOption.label}'),
+                        '${mealTypeOption.emoji} ${mealTypeLabel(mealTypeOption.id, l10n)}'),
                   ))
               .toList(),
           onChanged: onChanged,