flutter: Remove appBar backgroundColor and use MaterialApp primarySwatch instead

src/ui/flutter_app/lib/main.dart

@@ -25,6 +25,7 @@ import 'package:flutter/services.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:sanmill/generated/l10n.dart';
+import 'package:sanmill/style/colors.dart';
 import 'package:sanmill/widgets/navigation_home_screen.dart';
 import 'package:stack_trace/stack_trace.dart';
 
@@ -156,7 +157,7 @@ class _SanmillAppState extends State<SanmillApp> {
             languageCode: 'zh'), // Chinese *See Advanced Locales below*
         // ... other locales the app supports
       ],
-      theme: ThemeData(primarySwatch: Colors.green),
+      theme: ThemeData(primarySwatch: UIColors.appBarColor),
       debugShowCheckedModeBanner: false,
       home: WillPopScope(
         onWillPop: () async {

src/ui/flutter_app/lib/style/colors.dart

@@ -34,6 +34,8 @@ class UIColors {
   static var darkBackgroundColor = crusoeColor;
   static const lightBackgroundColor = papayaWhipColor;
 
+  static var appBarColor = UIColors.primaryColor;
+
   static var boardBackgroundColor = burlyWoodColor;
 
   static const darkTextPrimaryColor = Colors.white;

src/ui/flutter_app/lib/widgets/game_settings_page.dart

@@ -102,9 +102,9 @@ class _GameSettingsPageState extends State<GameSettingsPage> {
     return Scaffold(
       backgroundColor: UIColors.lightBackgroundColor,
       appBar: AppBar(
-          centerTitle: true,
-          title: Text(S.of(context).settings),
-          backgroundColor: UIColors.primaryColor),
+        centerTitle: true,
+        title: Text(S.of(context).settings),
+      ),
       body: SingleChildScrollView(
         padding: const EdgeInsets.all(16),
         child: Column(

src/ui/flutter_app/lib/widgets/personalization_settings_page.dart

@@ -175,9 +175,9 @@ class _PersonalizationSettingsPageState
     return Scaffold(
       backgroundColor: UIColors.lightBackgroundColor,
       appBar: AppBar(
-          centerTitle: true,
-          title: Text(S.of(context).personalization),
-          backgroundColor: UIColors.primaryColor),
+        centerTitle: true,
+        title: Text(S.of(context).personalization),
+      ),
       body: SingleChildScrollView(
         padding: const EdgeInsets.all(16),
         child: Column(