refactor(tests): replace 'final' with 'const' for improved performance in various test files

test/features/diary/presentation/widgets/add_product_button_widget_test.dart

@@ -24,7 +24,7 @@ void main() {
         theme: ThemeHelper().themeData(),
         home: BlocProvider<DiaryCubit>.value(
           value: mockCubit,
-          child: Scaffold(
+          child: const Scaffold(
             body: AddProductButtonWidget(),
           ),
         ),
@@ -32,7 +32,7 @@ void main() {
     }
 
     testWidgets('displays add product button widget', (tester) async {
-      final loadingState = DiaryState.loading();
+      const loadingState = DiaryState.loading();
       when(mockCubit.state).thenReturn(loadingState);
       when(mockCubit.stream).thenAnswer((_) => Stream.value(loadingState));
 

test/features/diary/presentation/widgets/chosen_diet_widget_content_test.dart

@@ -10,7 +10,7 @@ void main() {
     Widget createTestWidget(Widget child) {
       return MaterialApp(
         theme: ThemeHelper().themeData(),
-        localizationsDelegates: [
+        localizationsDelegates: const [
           S.delegate,
           GlobalMaterialLocalizations.delegate,
           GlobalWidgetsLocalizations.delegate,
@@ -26,7 +26,7 @@ void main() {
     testWidgets('displays chosen diet widget content', (tester) async {
       await tester.pumpWidget(
         createTestWidget(
-          ChosenDietWidgetContent(
+          const ChosenDietWidgetContent(
             currentDietDay: 5,
             dietName: 'Test Diet',
             dietDuration: 14,
@@ -42,7 +42,7 @@ void main() {
     testWidgets('displays current day and duration', (tester) async {
       await tester.pumpWidget(
         createTestWidget(
-          ChosenDietWidgetContent(
+          const ChosenDietWidgetContent(
             currentDietDay: 7,
             dietName: 'Test Diet',
             dietDuration: 21,
@@ -57,7 +57,7 @@ void main() {
     testWidgets('displays diet name with underline', (tester) async {
       await tester.pumpWidget(
         createTestWidget(
-          ChosenDietWidgetContent(
+          const ChosenDietWidgetContent(
             currentDietDay: 1,
             dietName: 'My Diet',
             dietDuration: 7,

test/features/diary/presentation/widgets/comment_container_test.dart

@@ -9,7 +9,7 @@ void main() {
       await tester.pumpWidget(
         MaterialApp(
           theme: ThemeHelper().themeData(),
-          home: Scaffold(
+          home: const Scaffold(
             body: CommentContainer(comment: 'Test comment'),
           ),
         ),
@@ -23,7 +23,7 @@ void main() {
       await tester.pumpWidget(
         MaterialApp(
           theme: ThemeHelper().themeData(),
-          home: Scaffold(
+          home: const Scaffold(
             body: CommentContainer(comment: ''),
           ),
         ),
@@ -37,7 +37,7 @@ void main() {
       await tester.pumpWidget(
         MaterialApp(
           theme: ThemeHelper().themeData(),
-          home: Scaffold(
+          home: const Scaffold(
             body: CommentContainer(comment: longComment),
           ),
         ),

test/features/diary/presentation/widgets/product_loader_widget_test.dart

@@ -7,7 +7,7 @@ void main() {
   group('ProductLoaderWidget', () {
     testWidgets('displays product loader widget', (tester) async {
       await tester.pumpWidget(
-        MaterialApp(
+        const MaterialApp(
           home: Scaffold(
             body: ProductLoaderWidget(),
           ),
@@ -20,7 +20,7 @@ void main() {
 
     testWidgets('displays ListTile with activity indicator', (tester) async {
       await tester.pumpWidget(
-        MaterialApp(
+        const MaterialApp(
           home: Scaffold(
             body: ProductLoaderWidget(),
           ),