update

lib/core/services/biometric_service.dart

@@ -0,0 +1,37 @@
+import 'package:local_auth/local_auth.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+class BiometricService {
+  static final _auth = LocalAuthentication();
+  static const _key = 'biometric_enabled';
+
+  static Future<bool> isAvailable() async {
+    final canCheck = await _auth.canCheckBiometrics;
+    final isSupported = await _auth.isDeviceSupported();
+    return canCheck && isSupported;
+  }
+
+  static Future<bool> isEnabled() async {
+    final prefs = await SharedPreferences.getInstance();
+    return prefs.getBool(_key) ?? false;
+  }
+
+  static Future<void> setEnabled(bool value) async {
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setBool(_key, value);
+  }
+
+  static Future<bool> authenticate() async {
+    try {
+      return await _auth.authenticate(
+        localizedReason: 'Confirm your identity to open Casha',
+        options: const AuthenticationOptions(
+          biometricOnly: false,
+          stickyAuth: true,
+        ),
+      );
+    } catch (_) {
+      return false;
+    }
+  }
+}

lib/features/settings/screen.dart

@@ -4,6 +4,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 import 'package:intl/intl.dart';
 import '../../core/constants.dart';
+import '../../core/services/biometric_service.dart';
 import '../../shared/utils/currency_utils.dart';
 import '../../shared/providers/amount_format_provider.dart';
 import '../dashboard/provider.dart';
@@ -387,6 +388,8 @@ class _SettingsScreenState extends ConsumerState<SettingsScreen> {
             ),
             const SizedBox(height: 16),
 
+            const _BiometricSection(),
+
             Container(
               padding: const EdgeInsets.all(20),
               decoration: BoxDecoration(
@@ -543,3 +546,106 @@ class _SettingsScreenState extends ConsumerState<SettingsScreen> {
     );
   }
 }
+
+class _BiometricSection extends StatefulWidget {
+  const _BiometricSection();
+
+  @override
+  State<_BiometricSection> createState() => _BiometricSectionState();
+}
+
+class _BiometricSectionState extends State<_BiometricSection> {
+  bool _available = false;
+  bool _enabled = false;
+  bool _loading = true;
+
+  @override
+  void initState() {
+    super.initState();
+    _load();
+  }
+
+  Future<void> _load() async {
+    final available = await BiometricService.isAvailable();
+    final enabled = await BiometricService.isEnabled();
+    if (mounted) {
+      setState(() {
+        _available = available;
+        _enabled = enabled;
+        _loading = false;
+      });
+    }
+  }
+
+  Future<void> _onToggle(bool val) async {
+    if (val) {
+      final ok = await BiometricService.authenticate();
+      if (!ok) return;
+    }
+    await BiometricService.setEnabled(val);
+    if (mounted) setState(() => _enabled = val);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    if (_loading || !_available) return const SizedBox.shrink();
+    
+    final isDark = Theme.of(context).brightness == Brightness.dark;
+    
+    return Column(
+      children: [
+        Container(
+          padding: const EdgeInsets.all(20),
+          decoration: BoxDecoration(
+            color: Theme.of(context).colorScheme.surface,
+            borderRadius: BorderRadius.circular(16),
+            border: isDark ? null : Border.all(color: const Color(0xFFDDDDEE), width: 1),
+          ),
+          child: Row(
+            children: [
+              Container(
+                padding: const EdgeInsets.all(10),
+                decoration: BoxDecoration(
+                  color: AppColors.accent.withOpacity(0.15),
+                  borderRadius: BorderRadius.circular(12),
+                ),
+                child: const Icon(
+                  Icons.fingerprint,
+                  color: AppColors.accent,
+                  size: 20,
+                ),
+              ),
+              const SizedBox(width: 12),
+              Expanded(
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    Text(
+                      'Biometric Lock',
+                      style: Theme.of(context).textTheme.titleMedium?.copyWith(
+                            fontWeight: FontWeight.w600,
+                            color: Theme.of(context).colorScheme.onSurface,
+                          ),
+                    ),
+                    Text(
+                      'Require fingerprint on app launch',
+                      style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                            color: Theme.of(context).colorScheme.onSurface.withOpacity(0.6),
+                          ),
+                    ),
+                  ],
+                ),
+              ),
+              Switch(
+                value: _enabled,
+                onChanged: _onToggle,
+                activeColor: const Color(0xFF7C6DED),
+              ),
+            ],
+          ),
+        ),
+        const SizedBox(height: 16),
+      ],
+    );
+  }
+}

lib/features/splash/screen.dart

@@ -1,6 +1,8 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:go_router/go_router.dart';
 import 'package:google_fonts/google_fonts.dart';
+import '../../core/services/biometric_service.dart';
 
 class SplashScreen extends StatefulWidget {
   const SplashScreen({super.key});
@@ -28,9 +30,17 @@ class _SplashScreenState extends State<SplashScreen> with SingleTickerProviderSt
 
     _controller.forward();
 
-    _controller.addStatusListener((status) {
+    _controller.addStatusListener((status) async {
       if (status == AnimationStatus.completed) {
         if (mounted) {
+          final isEnabled = await BiometricService.isEnabled();
+          if (isEnabled) {
+            final authenticated = await BiometricService.authenticate();
+            if (!authenticated) {
+              SystemNavigator.pop();
+              return;
+            }
+          }
           context.go('/dashboard');
         }
       }