refactor(theme): centralize theme customization in app.dart

- Add theme customization parameters in app.dart
- Update import statements for l10n
- Adjust theme settings in StatusPage
- TODO: Implement proper localization for retry button text

Author: fulleni

lib/app/view/app.dart

@@ -9,6 +9,7 @@ import 'package:flutter_news_app_mobile_client_full_source_code/app/config/app_e
 import 'package:flutter_news_app_mobile_client_full_source_code/app/services/app_status_service.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/app/services/demo_data_migration_service.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/authentication/bloc/authentication_bloc.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/l10n/app_localizations.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/l10n/l10n.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/router/router.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/status/view/view.dart';
@@ -207,8 +208,18 @@ class _AppViewState extends State<_AppView> {
             // It's wrapped in a basic MaterialApp to provide theme and l10n.
             return MaterialApp(
               debugShowCheckedModeBanner: false,
-              theme: lightTheme(),
-              darkTheme: darkTheme(),
+              theme: lightTheme(
+                scheme: FlexScheme.material,
+                appTextScaleFactor: AppTextScaleFactor.medium,
+                appFontWeight: AppFontWeight.regular,
+                fontFamily: null,
+              ),
+              darkTheme: darkTheme(
+                scheme: FlexScheme.material,
+                appTextScaleFactor: AppTextScaleFactor.medium,
+                appFontWeight: AppFontWeight.regular,
+                fontFamily: null,
+              ),
               themeMode: state.themeMode,
               localizationsDelegates: AppLocalizations.localizationsDelegates,
               supportedLocales: AppLocalizations.supportedLocales,
@@ -220,8 +231,18 @@ class _AppViewState extends State<_AppView> {
             // A mandatory update is required. Show the UpdateRequiredPage.
             return MaterialApp(
               debugShowCheckedModeBanner: false,
-              theme: lightTheme(),
-              darkTheme: darkTheme(),
+              theme: lightTheme(
+                scheme: FlexScheme.material,
+                appTextScaleFactor: AppTextScaleFactor.medium,
+                appFontWeight: AppFontWeight.regular,
+                fontFamily: null,
+              ),
+              darkTheme: darkTheme(
+                scheme: FlexScheme.material,
+                appTextScaleFactor: AppTextScaleFactor.medium,
+                appFontWeight: AppFontWeight.regular,
+                fontFamily: null,
+              ),
               themeMode: state.themeMode,
               localizationsDelegates: AppLocalizations.localizationsDelegates,
               supportedLocales: AppLocalizations.supportedLocales,
@@ -236,8 +257,18 @@ class _AppViewState extends State<_AppView> {
             // both the loading indicator and the retry mechanism.
             return MaterialApp(
               debugShowCheckedModeBanner: false,
-              theme: lightTheme(),
-              darkTheme: darkTheme(),
+              theme: lightTheme(
+                scheme: FlexScheme.material,
+                appTextScaleFactor: AppTextScaleFactor.medium,
+                appFontWeight: AppFontWeight.regular,
+                fontFamily: null,
+              ),
+              darkTheme: darkTheme(
+                scheme: FlexScheme.material,
+                appTextScaleFactor: AppTextScaleFactor.medium,
+                appFontWeight: AppFontWeight.regular,
+                fontFamily: null,
+              ),
               themeMode: state.themeMode,
               localizationsDelegates: AppLocalizations.localizationsDelegates,
               supportedLocales: AppLocalizations.supportedLocales,

lib/status/view/status_page.dart

@@ -1,4 +1,4 @@
-import 'package:core/core.dart';
+import 'package:core/core.dart' hide AppStatus;
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/app/bloc/app_bloc.dart';
@@ -24,7 +24,7 @@ class StatusPage extends StatelessWidget {
     return Scaffold(
       body: BlocBuilder<AppBloc, AppState>(
         builder: (context, state) {
-          final l10n = context.l10n;
+          final l10n = AppLocalizationsX(context).l10n;
 
           if (state.status == AppStatus.configFetching) {
             // While fetching configuration, display a clear loading indicator.
@@ -40,7 +40,7 @@ class StatusPage extends StatelessWidget {
           // This allows the user to recover from transient network issues.
           return FailureStateWidget(
             exception: const NetworkException(), // A generic network error
-            retryButtonText: l10n.retryButtonText,
+            retryButtonText: 'l10n.retryButtonText', //TODO(fulleni): localize me.
             onRetry: () {
               // Dispatch the event to AppBloc to re-trigger the fetch.
               context.read<AppBloc>().add(const AppConfigFetchRequested());