feat: reduce resume cooldown to 30s; add pull-to-refresh to News, Calendar; refresh chat on resume

lib/screens/chat/chat_screen.dart

@@ -16,12 +16,27 @@ class ChatScreen extends ConsumerStatefulWidget {
   ConsumerState<ChatScreen> createState() => _ChatScreenState();
 }
 
-class _ChatScreenState extends ConsumerState<ChatScreen> {
+class _ChatScreenState extends ConsumerState<ChatScreen>
+    with WidgetsBindingObserver {
   final _controller = TextEditingController();
   final _scrollController = ScrollController();
 
+  @override
+  void initState() {
+    super.initState();
+    WidgetsBinding.instance.addObserver(this);
+  }
+
+  @override
+  void didChangeAppLifecycleState(AppLifecycleState state) {
+    if (state == AppLifecycleState.resumed) {
+      ref.invalidate(messagesProvider(widget.conversationId));
+    }
+  }
+
   @override
   void dispose() {
+    WidgetsBinding.instance.removeObserver(this);
     _controller.dispose();
     _scrollController.dispose();
     // Exit voice mode if the user navigates away mid-session.