Implement password protection

lib/password_service.dart

@@ -0,0 +1,57 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+import 'package:traccar_client/l10n/app_localizations.dart';
+
+class PasswordService {
+  static final FlutterSecureStorage _secureStorage = const FlutterSecureStorage();
+  static const String _passwordKey = 'password';
+
+  static Future<bool> authenticate(BuildContext context) async {
+    if (!await _secureStorage.containsKey(key: _passwordKey)) return true;
+    final controller = TextEditingController();
+    bool? result;
+    if (context.mounted) {
+      result = await showDialog<bool>(
+        context: context,
+        builder: (context) => AlertDialog(
+          content: TextField(
+            controller: controller,
+            autofocus: true,
+            obscureText: true,
+            decoration: InputDecoration(labelText: AppLocalizations.of(context)!.passwordLabel),
+          ),
+          actions: [
+            TextButton(
+              onPressed: () => Navigator.pop(context, false),
+              child: Text(AppLocalizations.of(context)!.cancelButton),
+            ),
+            TextButton(
+              onPressed: () async {
+                final password = await _secureStorage.read(key: _passwordKey);
+                if (context.mounted) {
+                  Navigator.pop(context, password == controller.text);
+                }
+              },
+              child: Text(AppLocalizations.of(context)!.okButton),
+            ),
+          ],
+        ),
+      );
+    }
+    if (result != true && context.mounted) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text(AppLocalizations.of(context)!.passwordError)),
+      );
+      return false;
+    }
+    return result == true;
+  }
+
+  static Future<void> setPassword(String password) async {
+    if (password.isNotEmpty) {
+      await _secureStorage.write(key: _passwordKey, value: password);
+    } else {
+      await _secureStorage.delete(key: _passwordKey);
+    }
+  }
+}