feat: add utility functions for date and quantity formatting; refactor inventory and recipe screens to use new formatters

flutter/lib/features/inventory/presentation/create_inventory_screen.dart

@@ -3,6 +3,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 
 import '../../../core/api/api_error_mapper.dart';
+import '../../../core/utils/formatters.dart';
 import '../../../core/api/api_paths.dart';
 import '../../../core/api/api_providers.dart';
 import '../../../core/forms/form_options.dart';
@@ -142,10 +143,7 @@ class _CreateInventoryScreenState
     }
   }
 
-  String _formatDate(DateTime? dt) {
-    if (dt == null) return context.l10n.selectDateLabel;
-    return '${dt.year}-${dt.month.toString().padLeft(2, '0')}-${dt.day.toString().padLeft(2, '0')}';
-  }
+  String _formatDate(DateTime? dt) => formatDate(dt, fallback: context.l10n.selectDateLabel);
 
   @override
   Widget build(BuildContext context) {

flutter/lib/features/inventory/presentation/inventory_detail_screen.dart

@@ -3,6 +3,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 
 import '../../../core/api/api_error_mapper.dart';
+import '../../../core/utils/formatters.dart';
 import '../../../core/l10n/l10n.dart';
 import '../../../core/ui/async_state_views.dart';
 import '../../auth/data/auth_providers.dart';
@@ -77,14 +78,7 @@ class InventoryDetailScreen extends ConsumerWidget {
     );
   }
 
-  String _formatDate(String iso) {
-    try {
-      final dt = DateTime.parse(iso);
-      return '${dt.year}-${dt.month.toString().padLeft(2, '0')}-${dt.day.toString().padLeft(2, '0')}';
-    } catch (_) {
-      return iso;
-    }
-  }
+  String _formatDate(String iso) => formatDateString(iso);
 }
 
 class _DeleteButton extends ConsumerWidget {

flutter/lib/features/inventory/presentation/inventory_edit_screen.dart

@@ -3,6 +3,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 
 import '../../../core/api/api_error_mapper.dart';
+import '../../../core/utils/formatters.dart';
 import '../../../core/forms/form_options.dart';
 import '../../../core/l10n/l10n.dart';
 import '../../../core/ui/async_state_views.dart';
@@ -117,10 +118,7 @@ class _InventoryEditScreenState extends ConsumerState<InventoryEditScreen> {
     }
   }
 
-  String _formatDate(DateTime? dt) {
-    if (dt == null) return context.l10n.selectDateLabel;
-    return '${dt.year}-${dt.month.toString().padLeft(2, '0')}-${dt.day.toString().padLeft(2, '0')}';
-  }
+  String _formatDate(DateTime? dt) => formatDate(dt, fallback: context.l10n.selectDateLabel);
 
   @override
   Widget build(BuildContext context) {

flutter/lib/features/inventory/presentation/swipeable_inventory_tile.dart

@@ -3,6 +3,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 
 import '../../../core/api/api_error_mapper.dart';
+import '../../../core/utils/formatters.dart';
 import '../../auth/data/auth_providers.dart';
 import '../data/inventory_providers.dart';
 import '../domain/inventory_item.dart';
@@ -287,17 +288,9 @@ class _ForegroundTile extends ConsumerWidget {
     );
   }
 
-  String _fmtQty(double v) =>
-      v == v.roundToDouble() ? v.toStringAsFixed(0) : v.toStringAsFixed(1);
+  String _fmtQty(double v) => formatQuantity(v);
 
-  String _formatDate(String iso) {
-    try {
-      final dt = DateTime.parse(iso);
-      return '${dt.year}-${dt.month.toString().padLeft(2, '0')}-'
-          '${dt.day.toString().padLeft(2, '0')}';
-    } catch (_) {
-      return iso;
-    }
+  String _formatDate(String iso) => formatDateString(iso);
   }
 }
 

flutter/lib/features/meal_plan/presentation/meal_plan_screen.dart

@@ -6,6 +6,7 @@ import 'package:go_router/go_router.dart';
 import 'package:intl/intl.dart';
 
 import '../../../core/api/api_error_mapper.dart';
+import '../../../core/utils/formatters.dart';
 import '../../../core/l10n/l10n.dart';
 import '../../../core/ui/async_state_views.dart';
 import '../../auth/data/auth_providers.dart';
@@ -591,8 +592,5 @@ class _EnrichedShoppingItem {
     }
   }
 
-  String _formatQuantity(double value) {
-    final normalized = value == value.roundToDouble() ? value.toStringAsFixed(0) : value.toStringAsFixed(1);
-    return normalized.replaceAll(RegExp(r'\.0$'), '');
-  }
+  String _formatQuantity(double value) => formatQuantity(value);
 }

flutter/lib/features/recipes/presentation/create_recipe_screen.dart

@@ -4,6 +4,7 @@ import 'package:go_router/go_router.dart';
 
 import '../../../core/api/api_error_mapper.dart';
 import '../../../core/api/api_exception.dart';
+import '../../../core/utils/formatters.dart';
 import '../../../core/l10n/l10n.dart';
 import '../../auth/data/auth_providers.dart';
 import '../data/recipe_providers.dart';
@@ -305,11 +306,7 @@ class _CreateRecipeScreenState extends ConsumerState<CreateRecipeScreen> {
   }
 
   Widget _buildIngredientRow(int index, ParsedIngredient ing) {
-    final qtyStr = ing.quantity > 0
-        ? (ing.quantity == ing.quantity.truncateToDouble()
-            ? '${ing.quantity.toInt()} '
-            : '${ing.quantity} ')
-        : '';
+    final qtyStr = ing.quantity > 0 ? '${formatQuantity(ing.quantity)} ' : '';
     final unitStr = ing.unit.isNotEmpty ? '${ing.unit} ' : '';
     final noteStr = ing.note != null ? ' (${ing.note})' : '';
     final label = '$qtyStr$unitStr${ing.rawName}$noteStr';

flutter/lib/features/recipes/presentation/recipe_detail_screen.dart

@@ -4,6 +4,7 @@ import 'package:go_router/go_router.dart';
 
 import '../../../core/api/api_error_mapper.dart';
 import '../../../core/api/api_exception.dart';
+import '../../../core/utils/formatters.dart';
 import '../../../core/auth/jwt_decoder.dart';
 import '../../../core/l10n/l10n.dart';
 import '../../../core/ui/async_state_views.dart';
@@ -12,8 +13,7 @@ import '../data/recipe_providers.dart';
 import '../domain/recipe.dart';
 import '../domain/inventory_preview.dart';
 
-String _fmtQty(double v) =>
-    v == v.truncateToDouble() ? v.toInt().toString() : v.toString();
+String _fmtQty(double v) => formatQuantity(v);
 
 enum _ShareAction { share, unshare }
 

flutter/lib/features/recipes/presentation/recipe_edit_screen.dart

@@ -4,6 +4,7 @@ import 'package:go_router/go_router.dart';
 
 import '../../../core/api/api_error_mapper.dart';
 import '../../../core/api/api_exception.dart';
+import '../../../core/utils/formatters.dart';
 import '../../../core/api/api_paths.dart';
 import '../../../core/api/api_providers.dart';
 import '../../../core/forms/form_options.dart';
@@ -31,13 +32,10 @@ class _EditableIngredient {
         noteCtrl = TextEditingController(text: note);
 
   factory _EditableIngredient.fromRecipe(RecipeIngredient ingredient) {
-    final quantity = ingredient.quantity == ingredient.quantity.truncateToDouble()
-        ? ingredient.quantity.toInt().toString()
-        : ingredient.quantity.toString();
     return _EditableIngredient(
       productId: ingredient.productId,
       productName: ingredient.productName,
-      quantity: quantity,
+      quantity: formatQuantity(ingredient.quantity),
       unit: ingredient.unit,
       note: ingredient.note ?? '',
     );