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,
+  );
+}

lib/features/front_hall/presentation/widgets/dashboard_content.dart

@@ -4,6 +4,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:tatlock_ui/features/front_hall/data/models/system_stats_model.dart';
 import 'package:tatlock_ui/features/front_hall/presentation/providers/environment_provider.dart';
+import 'package:tatlock_ui/features/front_hall/presentation/providers/news_provider.dart';
 import 'package:tatlock_ui/features/front_hall/presentation/providers/system_stats_provider.dart';
 import 'package:tatlock_ui/shared/theme/stoplight_colors.dart';
 import 'package:tatlock_ui/shared/widgets/forecast_widget.dart';
@@ -25,6 +26,7 @@ class DashboardContent extends ConsumerStatefulWidget {
 class _DashboardContentState extends ConsumerState<DashboardContent> {
   Timer? _systemStatsTimer;
   Timer? _environmentTimer;
+  Timer? _newsTimer;
 
   /// Tracks if we've logged the environment API user (log once per session)
   static bool _hasLoggedEnvUser = false;
@@ -46,12 +48,18 @@ class _DashboardContentState extends ConsumerState<DashboardContent> {
       const Duration(hours: 1),
       (_) => ref.invalidate(environmentProvider),
     );
+    // Refresh news every 30 minutes
+    _newsTimer = Timer.periodic(
+      const Duration(minutes: 30),
+      (_) => ref.invalidate(newsProvider),
+    );
   }
 
   @override
   void dispose() {
     _systemStatsTimer?.cancel();
     _environmentTimer?.cancel();
+    _newsTimer?.cancel();
     super.dispose();
   }
 
@@ -60,6 +68,7 @@ class _DashboardContentState extends ConsumerState<DashboardContent> {
     final colorScheme = Theme.of(context).colorScheme;
     final systemStatsAsync = ref.watch(systemStatsProvider);
     final environmentAsync = ref.watch(environmentProvider);
+    final newsAsync = ref.watch(newsProvider);
 
     return ListView(
       padding: const EdgeInsets.all(16),
@@ -100,6 +109,14 @@ class _DashboardContentState extends ConsumerState<DashboardContent> {
         ),
         const SizedBox(height: 16),
 
+        // News Ticker - full width
+        newsAsync.when(
+          data: (newsData) => NewsTickerWidget(newsData: newsData),
+          loading: () => const NewsTickerWidget(),
+          error: (error, stack) => const NewsTickerWidget(),
+        ),
+        const SizedBox(height: 16),
+
         // System Stats - Gauges
         _SectionHeader(title: 'System Stats', icon: Icons.monitor_heart),
         const SizedBox(height: 8),