feat: meal tracking, dish recognition UX improvements, English AI prompts

Backend:
- Translate all recognition prompts (receipt, products, dish) from Russian to English
- Add lang parameter to Recognizer interface and pass locale.FromContext in handlers
- DishResult type uses candidates array for multi-candidate responses

Client:
- Add meal tracking: diary provider, date selector, meal type model
- DishResult parser: backward-compatible with legacy flat format and new candidates format
- DishResultScreen: sticky bottom button, full-width portion/meal-type inputs,
  КБЖУ disclaimer moved under nutrition card, add date field to diary POST body
- Recognition prompts now return dish/product names in user's preferred language
- Onboarding, profile, home screen visual updates

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

client/lib/features/scan/scan_screen.dart

@@ -12,11 +12,36 @@ final _recognitionServiceProvider = Provider<RecognitionService>((ref) {
 });
 
 /// Entry screen — lets the user choose how to add products.
-class ScanScreen extends ConsumerWidget {
+/// If [GoRouterState.extra] is a non-null String, it is treated as a meal type ID
+/// and the screen immediately opens the camera for dish recognition.
+class ScanScreen extends ConsumerStatefulWidget {
   const ScanScreen({super.key});
 
   @override
-  Widget build(BuildContext context, WidgetRef ref) {
+  ConsumerState<ScanScreen> createState() => _ScanScreenState();
+}
+
+class _ScanScreenState extends ConsumerState<ScanScreen> {
+  bool _autoStarted = false;
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    if (_autoStarted) return;
+    final mealType = GoRouterState.of(context).extra as String?;
+    if (mealType != null && mealType.isNotEmpty) {
+      _autoStarted = true;
+      // Defer to avoid calling context navigation during build.
+      WidgetsBinding.instance.addPostFrameCallback((_) {
+        if (mounted) {
+          _pickAndRecognize(context, _Mode.dish, mealType: mealType);
+        }
+      });
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(title: const Text('Добавить продукты')),
       body: ListView(
@@ -33,21 +58,21 @@ class ScanScreen extends ConsumerWidget {
             emoji: '🧾',
             title: 'Сфотографировать чек',
             subtitle: 'Распознаем все продукты из чека',
-            onTap: () => _pickAndRecognize(context, ref, _Mode.receipt),
+            onTap: () => _pickAndRecognize(context, _Mode.receipt),
           ),
           const SizedBox(height: 16),
           _ModeCard(
             emoji: '🥦',
             title: 'Сфотографировать продукты',
             subtitle: 'Холодильник, стол, полка — до 3 фото',
-            onTap: () => _pickAndRecognize(context, ref, _Mode.products),
+            onTap: () => _pickAndRecognize(context, _Mode.products),
           ),
           const SizedBox(height: 16),
           _ModeCard(
             emoji: '🍽️',
             title: 'Определить блюдо',
             subtitle: 'КБЖУ≈ по фото готового блюда',
-            onTap: () => _pickAndRecognize(context, ref, _Mode.dish),
+            onTap: () => _pickAndRecognize(context, _Mode.dish),
           ),
           const SizedBox(height: 16),
           _ModeCard(
@@ -63,9 +88,9 @@ class ScanScreen extends ConsumerWidget {
 
   Future<void> _pickAndRecognize(
     BuildContext context,
-    WidgetRef ref,
-    _Mode mode,
-  ) async {
+    _Mode mode, {
+    String? mealType,
+  }) async {
     final picker = ImagePicker();
 
     List<XFile> files = [];
@@ -120,11 +145,11 @@ class ScanScreen extends ConsumerWidget {
           final dish = await service.recognizeDish(files.first);
           if (context.mounted) {
             Navigator.pop(context);
-            context.push('/scan/dish', extra: dish);
+            context.push('/scan/dish', extra: {'dish': dish, 'meal_type': mealType});
           }
       }
-    } catch (e, s) {
-      debugPrint('Recognition error: $e\n$s');
+    } catch (recognitionError) {
+      debugPrint('Recognition error: $recognitionError');
       if (context.mounted) {
         Navigator.pop(context); // close loading
         ScaffoldMessenger.of(context).showSnackBar(