feat(ui_kit): add HeadlineSourceRow widget

- Create a new widget to display the source and publish date of a headline
- Implement tap functionality to navigate to source details
- Use timeago package to format publication date
- Apply theming and styling according to existing design guidelines

Author: fulleni

lib/shared/widgets/feed_core/headline_source_row.dart

@@ -0,0 +1,86 @@
+import 'package:core/core.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/ads/interstitial_ad_manager.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/router/routes.dart';
+import 'package:go_router/go_router.dart';
+import 'package:timeago/timeago.dart' as timeago;
+import 'package:ui_kit/ui_kit.dart';
+
+/// {@template headline_source_row}
+/// A widget to display the source and publish date of a headline.
+/// {@endtemplate}
+class HeadlineSourceRow extends StatelessWidget {
+  /// {@macro headline_source_row}
+  const HeadlineSourceRow({
+    required this.headline,
+    super.key,
+  });
+
+  /// The headline data to display.
+  final Headline headline;
+
+  Future<void> _handleEntityTap(BuildContext context) async {
+    await context.read<InterstitialAdManager>().onPotentialAdTrigger();
+    if (!context.mounted) return;
+    await context.pushNamed(
+      Routes.entityDetailsName,
+      pathParameters: {
+        'type': ContentType.source.name,
+        'id': headline.source.id,
+      },
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    final textTheme = theme.textTheme;
+    final colorScheme = theme.colorScheme;
+
+    final formattedDate = timeago.format(headline.createdAt);
+
+    final sourceTextStyle = textTheme.bodySmall?.copyWith(
+      color: colorScheme.onSurfaceVariant,
+      fontWeight: FontWeight.w500,
+    );
+
+    final dateTextStyle = textTheme.bodySmall?.copyWith(
+      color: colorScheme.onSurfaceVariant.withOpacity(0.7),
+    );
+
+    return Row(
+      mainAxisAlignment: MainAxisAlignment.spaceBetween,
+      children: [
+        Expanded(
+          child: InkWell(
+            onTap: () => _handleEntityTap(context),
+            child: Row(
+              mainAxisSize: MainAxisSize.min,
+              children: [
+                Icon(
+                  Icons.source_outlined,
+                  size: AppSpacing.md,
+                  color: colorScheme.onSurfaceVariant,
+                ),
+                const SizedBox(width: AppSpacing.xs),
+                Flexible(
+                  child: Text(
+                    headline.source.name,
+                    style: sourceTextStyle,
+                    overflow: TextOverflow.ellipsis,
+                  ),
+                ),
+              ],
+            ),
+          ),
+        ),
+        if (formattedDate.isNotEmpty)
+          Text(
+            formattedDate,
+            style: dateTextStyle,
+          ),
+      ],
+    );
+  }
+}