fix: use theme color for brightness mode compatibility

Author: anjakDev

lib/widgets/nutrition/ingredient_dialogs.dart

@@ -118,7 +118,7 @@ class IngredientDetails extends StatelessWidget {
                   Text(
                     ingredient.brand!,
                     style: Theme.of(context).textTheme.titleSmall?.copyWith(
-                      color: DefaultTextStyle.of(context).style.color?.withValues(alpha: 0.6),
+                      color: Theme.of(context).colorScheme.onSurfaceVariant,
                     ),
                   ),
               ],

lib/widgets/nutrition/widgets.dart

@@ -220,7 +220,9 @@ class _IngredientTypeaheadState extends ConsumerState<IngredientTypeahead> {
                       TextSpan(
                         text: '  ${ingredient.brand}',
                         style: TextStyle(
-                          color: DefaultTextStyle.of(context).style.color?.withValues(alpha: 0.6),
+                          color: Theme.of(
+                            context,
+                          ).colorScheme.onSurfaceVariant.withValues(alpha: 0.7),
                         ),
                       ),
                   ],