feat(app_configuration): add push notification settings form

- Implement PushNotificationSettingsForm widget for configuring push notification settings
- Add system status, primary provider, and delivery types configuration sections
- Use ExpansionTile for collapsible sections
- Implement SwitchListTile and SegmentedButton for user interactions
- Localize all strings using AppLocalizations

Author: fulleni

lib/app_configuration/widgets/push_notification_settings_form.dart

@@ -0,0 +1,188 @@
+import 'package:core/core.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_news_app_web_dashboard_full_source_code/l10n/l10n.dart';
+import 'package:flutter_news_app_web_dashboard_full_source_code/shared/extensions/push_notification_provider_l10n.dart';
+import 'package:flutter_news_app_web_dashboard_full_source_code/shared/extensions/push_notification_subscription_delivery_type_l10n.dart';
+import 'package:ui_kit/ui_kit.dart';
+
+/// {@template push_notification_settings_form}
+/// A form widget for configuring push notification settings.
+/// {@endtemplate}
+class PushNotificationSettingsForm extends StatelessWidget {
+  /// {@macro push_notification_settings_form}
+  const PushNotificationSettingsForm({
+    required this.remoteConfig,
+    required this.onConfigChanged,
+    super.key,
+  });
+
+  /// The current [RemoteConfig] object.
+  final RemoteConfig remoteConfig;
+
+  /// Callback to notify parent of changes to the [RemoteConfig].
+  final ValueChanged<RemoteConfig> onConfigChanged;
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = AppLocalizationsX(context).l10n;
+    final pushConfig = remoteConfig.pushNotificationConfig;
+
+    return SingleChildScrollView(
+      padding: const EdgeInsets.all(AppSpacing.lg),
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          ExpansionTile(
+            initiallyExpanded: true,
+            title: Text(l10n.pushNotificationSettingsTitle),
+            childrenPadding: const EdgeInsetsDirectional.only(
+              start: AppSpacing.lg,
+              top: AppSpacing.md,
+              bottom: AppSpacing.md,
+            ),
+            expandedCrossAxisAlignment: CrossAxisAlignment.start,
+            children: [
+              Text(
+                l10n.pushNotificationSettingsDescription,
+                style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                  color: Theme.of(
+                    context,
+                  ).colorScheme.onSurface.withOpacity(0.7),
+                ),
+              ),
+              const SizedBox(height: AppSpacing.lg),
+              _buildSystemStatusSection(context, l10n, pushConfig),
+              const SizedBox(height: AppSpacing.lg),
+              _buildPrimaryProviderSection(context, l10n, pushConfig),
+              const SizedBox(height: AppSpacing.lg),
+              _buildDeliveryTypesSection(context, l10n, pushConfig),
+            ],
+          ),
+        ],
+      ),
+    );
+  }
+
+  Widget _buildSystemStatusSection(
+    BuildContext context,
+    AppLocalizations l10n,
+    PushNotificationConfig pushConfig,
+  ) {
+    return ExpansionTile(
+      title: Text(l10n.pushNotificationSystemStatusTitle),
+      childrenPadding: const EdgeInsets.symmetric(
+        horizontal: AppSpacing.lg,
+        vertical: AppSpacing.md,
+      ),
+      children: [
+        SwitchListTile(
+          title: Text(l10n.enabledLabel),
+          subtitle: Text(l10n.pushNotificationSystemStatusDescription),
+          value: pushConfig.enabled,
+          onChanged: (value) {
+            onConfigChanged(
+              remoteConfig.copyWith(
+                pushNotificationConfig: pushConfig.copyWith(enabled: value),
+              ),
+            );
+          },
+        ),
+      ],
+    );
+  }
+
+  Widget _buildPrimaryProviderSection(
+    BuildContext context,
+    AppLocalizations l10n,
+    PushNotificationConfig pushConfig,
+  ) {
+    return ExpansionTile(
+      title: Text(l10n.pushNotificationPrimaryProviderTitle),
+      childrenPadding: const EdgeInsets.symmetric(
+        horizontal: AppSpacing.lg,
+        vertical: AppSpacing.md,
+      ),
+      expandedCrossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        Text(
+          l10n.pushNotificationPrimaryProviderDescription,
+          style: Theme.of(context).textTheme.bodySmall?.copyWith(
+            color: Theme.of(context).colorScheme.onSurface.withOpacity(0.7),
+          ),
+        ),
+        const SizedBox(height: AppSpacing.lg),
+        SegmentedButton<PushNotificationProvider>(
+          segments: PushNotificationProvider.values
+              .map(
+                (provider) => ButtonSegment<PushNotificationProvider>(
+                  value: provider,
+                  label: Text(provider.l10n(context)),
+                ),
+              )
+              .toList(),
+          selected: {pushConfig.primaryProvider},
+          onSelectionChanged: (newSelection) {
+            onConfigChanged(
+              remoteConfig.copyWith(
+                pushNotificationConfig: pushConfig.copyWith(
+                  primaryProvider: newSelection.first,
+                ),
+              ),
+            );
+          },
+        ),
+      ],
+    );
+  }
+
+  Widget _buildDeliveryTypesSection(
+    BuildContext context,
+    AppLocalizations l10n,
+    PushNotificationConfig pushConfig,
+  ) {
+    return ExpansionTile(
+      title: Text(l10n.pushNotificationDeliveryTypesTitle),
+      childrenPadding: const EdgeInsets.symmetric(
+        horizontal: AppSpacing.lg,
+        vertical: AppSpacing.md,
+      ),
+      expandedCrossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        Text(
+          l10n.pushNotificationDeliveryTypesDescription,
+          style: Theme.of(context).textTheme.bodySmall?.copyWith(
+            color: Theme.of(context).colorScheme.onSurface.withOpacity(0.7),
+          ),
+        ),
+        const SizedBox(height: AppSpacing.lg),
+        Column(
+          children: PushNotificationSubscriptionDeliveryType.values
+              .map(
+                (type) => SwitchListTile(
+                  title: Text(type.l10n(context)),
+                  value: pushConfig.deliveryConfigs[type] ?? false,
+                  onChanged: (value) {
+                    final newDeliveryConfigs =
+                        Map<
+                          PushNotificationSubscriptionDeliveryType,
+                          bool
+                        >.from(
+                          pushConfig.deliveryConfigs,
+                        );
+                    newDeliveryConfigs[type] = value;
+                    onConfigChanged(
+                      remoteConfig.copyWith(
+                        pushNotificationConfig: pushConfig.copyWith(
+                          deliveryConfigs: newDeliveryConfigs,
+                        ),
+                      ),
+                    );
+                  },
+                ),
+              )
+              .toList(),
+        ),
+      ],
+    );
+  }
+}