update

lib/app/app.dart

@@ -0,0 +1,17 @@
+import 'package:flutter/material.dart';
+import 'router.dart';
+import 'theme.dart';
+
+class App extends StatelessWidget {
+  const App({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp.router(
+      title: 'Finance Tracker',
+      debugShowCheckedModeBanner: false,
+      theme: buildAppTheme(),
+      routerConfig: appRouter,
+    );
+  }
+}

lib/app/router.dart

@@ -0,0 +1,79 @@
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+import '../features/dashboard/screen.dart';
+import '../features/add_transaction/screen.dart';
+import '../features/categories/screen.dart';
+
+final _shellKey = GlobalKey<NavigatorState>();
+
+final appRouter = GoRouter(
+  initialLocation: '/dashboard',
+  routes: [
+    ShellRoute(
+      navigatorKey: _shellKey,
+      builder: (context, state, child) => AppShell(child: child),
+      routes: [
+        GoRoute(
+          path: '/dashboard',
+          pageBuilder: (context, state) => const NoTransitionPage(
+            child: DashboardScreen(),
+          ),
+        ),
+        GoRoute(
+          path: '/categories',
+          pageBuilder: (context, state) => const NoTransitionPage(
+            child: CategoriesScreen(),
+          ),
+        ),
+      ],
+    ),
+    GoRoute(
+      path: '/add',
+      builder: (context, state) => const AddTransactionScreen(),
+    ),
+  ],
+);
+
+class AppShell extends StatelessWidget {
+  final Widget child;
+  const AppShell({super.key, required this.child});
+
+  int _locationToIndex(BuildContext context) {
+    final location = GoRouterState.of(context).uri.toString();
+    if (location.startsWith('/categories')) return 1;
+    return 0;
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final idx = _locationToIndex(context);
+    return Scaffold(
+      body: child,
+      floatingActionButton: FloatingActionButton(
+        onPressed: () => context.push('/add'),
+        backgroundColor: const Color(0xFF7C6DED),
+        child: const Icon(Icons.add, color: Colors.white),
+      ),
+      floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
+      bottomNavigationBar: NavigationBar(
+        selectedIndex: idx,
+        onDestinationSelected: (i) {
+          if (i == 0) context.go('/dashboard');
+          if (i == 1) context.go('/categories');
+        },
+        destinations: const [
+          NavigationDestination(
+            icon: Icon(Icons.dashboard_outlined),
+            selectedIcon: Icon(Icons.dashboard_rounded),
+            label: 'Dashboard',
+          ),
+          NavigationDestination(
+            icon: Icon(Icons.pie_chart_outline_rounded),
+            selectedIcon: Icon(Icons.pie_chart_rounded),
+            label: 'Categories',
+          ),
+        ],
+      ),
+    );
+  }
+}

lib/app/theme.dart

@@ -0,0 +1,101 @@
+import 'package:flutter/material.dart';
+import 'package:google_fonts/google_fonts.dart';
+import '../core/constants.dart';
+
+ThemeData buildAppTheme() {
+  final base = ThemeData.dark(useMaterial3: true);
+  final textTheme = GoogleFonts.poppinsTextTheme(base.textTheme).apply(
+    bodyColor: AppColors.textPrimary,
+    displayColor: AppColors.textPrimary,
+  );
+
+  return base.copyWith(
+    textTheme: textTheme,
+    scaffoldBackgroundColor: AppColors.background,
+    colorScheme: const ColorScheme.dark(
+      surface: AppColors.surface,
+      primary: AppColors.accent,
+      secondary: AppColors.accent,
+      onPrimary: Colors.white,
+      onSurface: AppColors.textPrimary,
+    ),
+    cardTheme: CardThemeData(
+      color: AppColors.surface,
+      elevation: 0,
+      shape: RoundedRectangleBorder(
+        borderRadius: BorderRadius.circular(16),
+      ),
+      margin: EdgeInsets.zero,
+    ),
+    appBarTheme: AppBarTheme(
+      backgroundColor: AppColors.background,
+      elevation: 0,
+      centerTitle: false,
+      titleTextStyle: GoogleFonts.poppins(
+        color: AppColors.textPrimary,
+        fontSize: 20,
+        fontWeight: FontWeight.w600,
+      ),
+      iconTheme: const IconThemeData(color: AppColors.textPrimary),
+    ),
+    navigationBarTheme: NavigationBarThemeData(
+      backgroundColor: AppColors.surface,
+      indicatorColor: AppColors.accent.withOpacity(0.2),
+      labelTextStyle: WidgetStateProperty.resolveWith((states) {
+        if (states.contains(WidgetState.selected)) {
+          return GoogleFonts.poppins(
+            color: AppColors.accent,
+            fontSize: 12,
+            fontWeight: FontWeight.w600,
+          );
+        }
+        return GoogleFonts.poppins(
+          color: AppColors.textSecondary,
+          fontSize: 12,
+        );
+      }),
+      iconTheme: WidgetStateProperty.resolveWith((states) {
+        if (states.contains(WidgetState.selected)) {
+          return const IconThemeData(color: AppColors.accent);
+        }
+        return const IconThemeData(color: AppColors.textSecondary);
+      }),
+    ),
+    inputDecorationTheme: InputDecorationTheme(
+      filled: true,
+      fillColor: AppColors.surface,
+      border: OutlineInputBorder(
+        borderRadius: BorderRadius.circular(12),
+        borderSide: const BorderSide(color: AppColors.divider),
+      ),
+      enabledBorder: OutlineInputBorder(
+        borderRadius: BorderRadius.circular(12),
+        borderSide: const BorderSide(color: AppColors.divider),
+      ),
+      focusedBorder: OutlineInputBorder(
+        borderRadius: BorderRadius.circular(12),
+        borderSide: const BorderSide(color: AppColors.accent, width: 1.5),
+      ),
+      labelStyle: const TextStyle(color: AppColors.textSecondary),
+      hintStyle: const TextStyle(color: AppColors.textSecondary),
+    ),
+    elevatedButtonTheme: ElevatedButtonThemeData(
+      style: ElevatedButton.styleFrom(
+        backgroundColor: AppColors.accent,
+        foregroundColor: Colors.white,
+        minimumSize: const Size(double.infinity, 52),
+        shape: RoundedRectangleBorder(
+          borderRadius: BorderRadius.circular(14),
+        ),
+        textStyle: GoogleFonts.poppins(
+          fontSize: 16,
+          fontWeight: FontWeight.w600,
+        ),
+      ),
+    ),
+    dividerTheme: const DividerThemeData(
+      color: AppColors.divider,
+      thickness: 1,
+    ),
+  );
+}