fix: eliminate pull-to-refresh flicker by holding stale data during re-fetch

lib/providers/calendar_provider.dart

@@ -56,6 +56,17 @@ class CalendarNotifier extends AsyncNotifier<CalendarState> {
     );
   }
 
+  /// Re-fetch events for the current range without clearing state (no flicker).
+  Future<void> refresh() async {
+    final current = state.value;
+    if (current == null) return;
+    final events = await ref.read(eventsApiProvider).getEvents(
+      current.loadedRange.start,
+      current.loadedRange.end,
+    );
+    state = AsyncData(current.copyWith(eventsByDay: _groupByDay(events)));
+  }
+
   /// Synchronously updates selectedDay and focusedMonth. No API call.
   void selectDay(DateTime day) {
     final current = state.value;

lib/providers/chat_provider.dart

@@ -58,6 +58,12 @@ class ConversationsNotifier extends AsyncNotifier<List<Conversation>> {
     ]);
   }
 
+  /// Re-fetch conversations without clearing the current list (no flicker).
+  Future<void> refresh() async {
+    final fresh = await ref.read(chatRepositoryProvider).getConversations();
+    state = AsyncData(fresh);
+  }
+
   // Called after a message is sent to patch the server-generated title
   // in-place without triggering a full reload or loading state.
   void patchConversation(Conversation updated) {
@@ -86,6 +92,13 @@ class MessagesNotifier extends AsyncNotifier<List<Message>> {
     return messages;
   }
 
+  /// Re-fetch messages without clearing the current list (no flicker).
+  Future<void> refresh() async {
+    final (_, messages) =
+        await ref.read(chatRepositoryProvider).getMessages(_convId);
+    state = AsyncData(messages);
+  }
+
   Future<void> sendMessage(String content) async {
     final convId = _convId;
     final repo = ref.read(chatRepositoryProvider);

lib/providers/news_provider.dart

@@ -71,6 +71,25 @@ class NewsNotifier extends AsyncNotifier<NewsState> {
     );
   }
 
+  /// Re-fetch the first page without clearing state (no flicker).
+  Future<void> refresh() async {
+    final current = state.value;
+    final items = await ref.read(newsApiProvider).getNewsItems(
+          days: 90,
+          limit: _limit,
+          offset: 0,
+          feedId: current?.selectedFeedId,
+        );
+    state = AsyncData(NewsState(
+      items: items,
+      offset: items.length,
+      hasMore: items.length == _limit,
+      loadingMore: false,
+      selectedFeedId: current?.selectedFeedId,
+      reactions: {for (final item in items) item.id: item.reaction},
+    ));
+  }
+
   Future<void> loadMore() async {
     final current = state.value;
     if (current == null || current.loadingMore || !current.hasMore) return;

lib/providers/projects_provider.dart

@@ -15,6 +15,12 @@ class ProjectsNotifier extends AsyncNotifier<List<Project>> {
         .getAll(sort: 'updated_at', order: 'desc');
   }
 
+  Future<void> refresh() async {
+    final fresh = await ref.read(projectsRepositoryProvider)
+        .getAll(sort: 'updated_at', order: 'desc');
+    state = AsyncData(fresh);
+  }
+
   Future<Project> create({
     required String title,
     String? description,

lib/providers/tasks_provider.dart

@@ -17,6 +17,11 @@ class TasksNotifier extends AsyncNotifier<List<Task>> {
     return ref.watch(tasksRepositoryProvider).getAll();
   }
 
+  Future<void> refresh() async {
+    final fresh = await ref.read(tasksRepositoryProvider).getAll();
+    state = AsyncData(fresh);
+  }
+
   Future<Task> create({
     required String title,
     String? description,