style(app_configuration): adjust subtitle text style for better visibility

- Update subtitle text style in FeaturesConfigurationTab and CommunityConfigForm
- Apply onSurface color with 0.7 opacity for better contrast and readability
- Extract subtitle style to a variable for reuse and consistency

Author: fulleni

lib/app_configuration/view/tabs/features_configuration_tab.dart

@@ -255,7 +255,14 @@ class _FeaturesConfigurationTabState extends State<FeaturesConfigurationTab> {
             return ExpansionTile(
               key: ValueKey('communityTile_$expandedIndex'),
               title: Text(l10n.communityAndEngagementTitle),
-              subtitle: Text(l10n.communityAndEngagementDescription),
+              subtitle: Text(
+                l10n.communityAndEngagementDescription,
+                style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                  color: Theme.of(
+                    context,
+                  ).colorScheme.onSurface.withOpacity(0.7),
+                ),
+              ),
               onExpansionChanged: (isExpanded) {
                 _expandedTileIndex.value = isExpanded ? tileIndex : null;
               },

lib/app_configuration/widgets/community_config_form.dart

@@ -30,13 +30,19 @@ class CommunityConfigForm extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final l10n = AppLocalizationsX(context).l10n;
+    final subtitleStyle = Theme.of(context).textTheme.bodySmall?.copyWith(
+      color: Theme.of(context).colorScheme.onSurface.withOpacity(0.7),
+    );
 
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
         ExpansionTile(
           title: Text(l10n.userEngagementTitle),
-          subtitle: Text(l10n.userEngagementDescription),
+          subtitle: Text(
+            l10n.userEngagementDescription,
+            style: subtitleStyle,
+          ),
           childrenPadding: const EdgeInsetsDirectional.only(
             start: AppSpacing.lg,
             top: AppSpacing.md,
@@ -53,7 +59,10 @@ class CommunityConfigForm extends StatelessWidget {
         const SizedBox(height: AppSpacing.lg),
         ExpansionTile(
           title: Text(l10n.contentReportingTitle),
-          subtitle: Text(l10n.contentReportingDescription),
+          subtitle: Text(
+            l10n.contentReportingDescription,
+            style: subtitleStyle,
+          ),
           childrenPadding: const EdgeInsetsDirectional.only(
             start: AppSpacing.lg,
             top: AppSpacing.md,
@@ -70,7 +79,10 @@ class CommunityConfigForm extends StatelessWidget {
         const SizedBox(height: AppSpacing.lg),
         ExpansionTile(
           title: Text(l10n.appFeedbackFunnelTitle),
-          subtitle: Text(l10n.appFeedbackFunnelDescription),
+          subtitle: Text(
+            l10n.appFeedbackFunnelDescription,
+            style: subtitleStyle,
+          ),
           children: [
             AppReviewSettingsForm(
               remoteConfig: remoteConfig,