feat(client_app): open privacy policy in in-app webview

Add a reusable WebPageScreen (webview_flutter host with close button +
progress bar, no nav interception) and wire the profile 'kebijakan privasi'
menu item to open https://mybestieindonesia.com/privacy in it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

client_app/lib/features/profile/profile_screen.dart

@@ -3,6 +3,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 import '../../core/auth/auth_notifier.dart';
 import '../../core/theme/halo_tokens.dart';
+import '../../core/widgets/web_page_screen.dart';
 import '../home/widgets/halo_tab_bar.dart';
 
 /// "Kamu" tab — profile screen.
@@ -78,7 +79,14 @@ class ProfileScreen extends ConsumerWidget {
                     _MenuItemData(
                       icon: Icons.lock_outline,
                       label: 'kebijakan privasi',
-                      onTap: () {},
+                      onTap: () => Navigator.of(context).push(
+                        MaterialPageRoute(
+                          builder: (_) => const WebPageScreen(
+                            url: 'https://mybestieindonesia.com/privacy',
+                            title: 'kebijakan privasi',
+                          ),
+                        ),
+                      ),
                     ),
                   ]),
                   const SizedBox(height: 16),