Enable profiles switch UI

lib/services/profiles_feature_service.dart

@@ -0,0 +1,54 @@
+import 'package:shared_preferences/shared_preferences.dart';
+
+class ProfilesFeatureService {
+  static const String enabledKey = 'profiles_enabled';
+
+  static Future<bool> isEnabled() async {
+    final prefs = await SharedPreferences.getInstance();
+    return prefs.getBool(enabledKey) ?? false;
+  }
+
+  static Future<void> setEnabled(bool enabled) async {
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setBool(enabledKey, enabled);
+  }
+}
+
+class ProfileStorageScope {
+  static bool _profilesEnabled = false;
+  static String _activeProfileId = 'default';
+
+  static Future<void> bootstrap({
+    required bool profilesEnabled,
+    required String activeProfileId,
+  }) async {
+    _profilesEnabled = profilesEnabled;
+    _activeProfileId = activeProfileId;
+  }
+
+  static void setScope({
+    required bool profilesEnabled,
+    required String activeProfileId,
+  }) {
+    _profilesEnabled = profilesEnabled;
+    _activeProfileId = activeProfileId;
+  }
+
+  static bool get profilesEnabled => _profilesEnabled;
+  static String get activeProfileId => _activeProfileId;
+
+  static String? get effectiveNamespace {
+    if (!_profilesEnabled || _activeProfileId == 'default') {
+      return null;
+    }
+    return _activeProfileId;
+  }
+
+  static String scopedKey(String baseKey, {String? namespace}) {
+    final scope = namespace ?? effectiveNamespace;
+    if (scope == null || scope.isEmpty) {
+      return baseKey;
+    }
+    return 'profile.$scope.$baseKey';
+  }
+}