feat: add news ticker widget for scrolling headlines

- Add NewsTickerWidget with horizontal auto-scrolling at 40px/sec
- Add NewsData and NewsHeadline Freezed models
- Add news datasource fetching from /tools/news endpoint
- Add news provider with 30-minute auto-refresh
- Place ticker between Welcome card and System Stats on dashboard
- Show placeholder headlines when no data (italic, muted style)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/features/front_hall/presentation/providers/news_provider.dart

@@ -0,0 +1,27 @@
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+import 'package:tatlock_ui/features/front_hall/data/datasources/news_datasource.dart';
+import 'package:tatlock_ui/features/front_hall/data/models/news_model.dart';
+
+part 'news_provider.g.dart';
+
+/// Fetches news headlines from Core API.
+///
+/// Auto-invalidates to keep data fresh.
+/// News data in Qdrant has TTL, so periodic refresh is reasonable.
+@riverpod
+Future<NewsData> news(Ref ref) async {
+  final datasource = ref.watch(newsDatasourceProvider);
+  return datasource.getNews();
+}
+
+/// Provides whether news data is available.
+///
+/// Used for conditional rendering of NewsTickerWidget.
+@riverpod
+bool hasNews(Ref ref) {
+  final asyncValue = ref.watch(newsProvider);
+  return asyncValue.maybeWhen(
+    data: (data) => data.headlines.isNotEmpty,
+    orElse: () => false,
+  );
+}