Move flutter app into root of repo

lib/main.dart

@@ -0,0 +1,103 @@
+// ignore_for_file: prefer_const_constructors, prefer_const_literals_to_create_immutables
+
+import 'package:flutter/material.dart';
+import 'package:provider/provider.dart';
+import 'days_enum.dart';
+
+void main() {
+  runApp(MyApp());
+}
+
+class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return ChangeNotifierProvider(
+      create: (context) => MyAppState(),
+      child: MaterialApp(
+        title: 'Advent of Code 2025',
+        theme: ThemeData(
+          useMaterial3: true,
+          colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepOrange),
+        ),
+        home: MyHomePage(),
+      ),
+    );
+  }
+}
+
+class MyAppState extends ChangeNotifier {
+}
+
+class MyHomePage extends StatefulWidget {
+  @override
+  State<MyHomePage> createState() => _MyHomePageState();
+}
+
+class _MyHomePageState extends State<MyHomePage> {
+  var selectedIndex = 0;
+
+  @override
+  Widget build(BuildContext context) {
+    // Manage days and create items list of a pages.
+    final days = [AdventOfCodeDays.day1, AdventOfCodeDays.day2];
+    List<NavigationRailDestination> dayItems = [];
+    for (var day in days) {
+      dayItems.add(
+        NavigationRailDestination(
+          icon: Icon(Icons.arrow_forward_ios),
+          label: Text(day.title),
+        ),
+      );
+    }
+    var colorScheme = Theme.of(context).colorScheme;
+
+    Widget page = DayPage();
+
+    // The container for the current page, with its background color
+    // and subtle switching animation.
+    var mainArea = ColoredBox(
+      color: colorScheme.surfaceContainerHighest,
+      child: AnimatedSwitcher(
+        duration: Duration(milliseconds: 200),
+        child: page,
+      ),
+    );
+
+    return Scaffold(
+      body: LayoutBuilder(
+        builder: (context, constraints) {
+          return Row(
+            children: [
+              SafeArea(
+                child: NavigationRail(
+                  extended: constraints.maxWidth >= 600,
+                  destinations: dayItems,
+                  selectedIndex: selectedIndex,
+                  onDestinationSelected: (value) {
+                    setState(() {
+                      selectedIndex = value;
+                    });
+                  },
+                ),
+              ),
+              Expanded(child: mainArea),
+            ],
+          );
+        },
+      ),
+    );
+  }
+}
+
+class DayPage extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      children: [
+        Row(children: [SizedBox(width: 10)]),
+      ],
+    );
+  }
+}