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/data/datasources/news_datasource.dart

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+import 'package:dio/dio.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+import 'package:tatlock_ui/core/api/api_client.dart';
+import 'package:tatlock_ui/features/front_hall/data/models/news_model.dart';
+
+part 'news_datasource.g.dart';
+
+/// Data source for news data operations.
+///
+/// Fetches news headlines from Core API.
+class NewsDatasource {
+  NewsDatasource(this._dio);
+
+  final Dio _dio;
+
+  static const _basePath = '/tools/news';
+
+  /// Gets current news headlines.
+  ///
+  /// Returns headlines for the news ticker.
+  Future<NewsData> getNews() async {
+    final response = await _dio.get<Map<String, dynamic>>(_basePath);
+    final data = response.data;
+
+    if (data == null) {
+      throw Exception('Failed to fetch news data');
+    }
+
+    return NewsData.fromJson(data);
+  }
+}
+
+/// Provides the news datasource.
+@riverpod
+NewsDatasource newsDatasource(Ref ref) {
+  final dio = ref.watch(coreApiClientProvider);
+  return NewsDatasource(dio);
+}

lib/features/front_hall/data/models/news_model.dart

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+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'news_model.freezed.dart';
+part 'news_model.g.dart';
+
+/// News response from Core API.
+/// Contains headlines for the news ticker.
+@freezed
+sealed class NewsData with _$NewsData {
+  const factory NewsData({
+    required List<NewsHeadline> headlines,
+    String? category,
+    List<String>? sources,
+    @JsonKey(name: 'updated_at') required DateTime updatedAt,
+    String? user,
+  }) = _NewsData;
+
+  factory NewsData.fromJson(Map<String, dynamic> json) =>
+      _$NewsDataFromJson(json);
+}
+
+/// Single news headline.
+@freezed
+sealed class NewsHeadline with _$NewsHeadline {
+  const factory NewsHeadline({
+    required String title,
+    String? description,
+    String? source,
+    String? url,
+  }) = _NewsHeadline;
+
+  factory NewsHeadline.fromJson(Map<String, dynamic> json) =>
+      _$NewsHeadlineFromJson(json);
+}