feat: Implement home screen with navigation and update login flow

lib/screens/home_screen.dart

@@ -0,0 +1,31 @@
+import 'package:flutter/material.dart';
+import 'schedule_screen.dart';
+import 'profile_screen.dart';
+
+class HomeScreen extends StatefulWidget {
+  @override
+  _HomeScreenState createState() => _HomeScreenState();
+}
+
+class _HomeScreenState extends State<HomeScreen> {
+  int _idx = 0;
+  final _pages = [ScheduleScreen(), ProfileScreen()];
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: _pages[_idx],
+      bottomNavigationBar: BottomNavigationBar(
+        currentIndex: _idx,
+        backgroundColor: Color(0xFF0c0a0a),
+        selectedItemColor: Color(0xFFA24BFA),
+        unselectedItemColor: Colors.white70,
+        items: [
+          BottomNavigationBarItem(icon: Icon(Icons.calendar_today), label: 'Beosztás'),
+          BottomNavigationBarItem(icon: Icon(Icons.person), label: 'Profil'),
+        ],
+        onTap: (i) => setState(() { _idx = i; }),
+      ),
+    );
+  }
+}