Add local backup/restore: encrypted .enc export to Download/loginvault, restore from list (no file_picker to avoid SDK conflict)

lib/settings_screen.dart

@@ -3,6 +3,7 @@ import 'package:flutter/services.dart';
 import 'package:login_vault_app/auth_service.dart';
 import 'package:login_vault_app/auth_screen.dart';
 import 'package:login_vault_app/theme_provider.dart';
+import 'package:login_vault_app/backup_service.dart';
 
 /// Settings: change app password, switch theme (dark/system), session timeout,
 /// fingerprint toggle, and Exit.
@@ -72,6 +73,73 @@ class _SettingsScreenState extends State<SettingsScreen> {
     _newCtrl.clear();
   }
 
+  Future<void> _backup() async {
+    try {
+      final path = await BackupService.exportEncrypted(widget.auth);
+      if (mounted) {
+        setState(() {
+          _msg = 'Backup tersimpan: $path';
+          _msgColor = Colors.green;
+        });
+      }
+    } catch (e) {
+      if (mounted) {
+        setState(() {
+          _msg = 'Backup gagal: $e';
+          _msgColor = Colors.red;
+        });
+      }
+    }
+  }
+
+  Future<void> _restore() async {
+    try {
+      final backups = await BackupService.listBackups();
+      if (backups.isEmpty) {
+        if (mounted) {
+          setState(() {
+            _msg = 'Tidak ada file backup di folder Download/loginvault';
+            _msgColor = Colors.red;
+          });
+        }
+        return;
+      }
+      if (!mounted) return;
+      final chosen = await showDialog<String>(
+        context: context,
+        builder: (ctx) => AlertDialog(
+          title: const Text('Pilih file backup'),
+          content: SizedBox(
+            width: double.maxFinite,
+            child: ListView.builder(
+              shrinkWrap: true,
+              itemCount: backups.length,
+              itemBuilder: (_, i) => ListTile(
+                title: Text(backups[i].path.split('/').last),
+                onTap: () => Navigator.of(ctx).pop(backups[i].path),
+              ),
+            ),
+          ),
+        ),
+      );
+      if (chosen == null) return;
+      final count = await BackupService.importEncrypted(widget.auth, chosen);
+      if (mounted) {
+        setState(() {
+          _msg = 'Restore berhasil: $count entri';
+          _msgColor = Colors.green;
+        });
+      }
+    } catch (e) {
+      if (mounted) {
+        setState(() {
+          _msg = 'Restore gagal: $e';
+          _msgColor = Colors.red;
+        });
+      }
+    }
+  }
+
   Future<void> _toggleBiometric(bool value) async {
     if (value && !_biometricAvailable) {
       setState(() {
@@ -209,6 +277,22 @@ class _SettingsScreenState extends State<SettingsScreen> {
               child: Text(_msg!, style: TextStyle(color: _msgColor)),
             ),
           const Divider(),
+          const Text('Backup & Restore',
+              style: TextStyle(fontWeight: FontWeight.bold)),
+          ListTile(
+            leading: const Icon(Icons.backup),
+            title: const Text('Backup ke file (lokal)'),
+            subtitle: const Text(
+                'Simpan vault terenkripsi ke folder Download. Bisa dipindah ke Drive manual.'),
+            onTap: _backup,
+          ),
+          ListTile(
+            leading: const Icon(Icons.restore),
+            title: const Text('Restore dari file'),
+            subtitle: const Text('Pilih file backup .enc untuk dikembalikan.'),
+            onTap: _restore,
+          ),
+          const Divider(),
           ListTile(
             leading: const Icon(Icons.exit_to_app),
             title: const Text('Keluar (Exit)'),