simplify: dedupe boilerplate and remove dead code across all layers

lib/view/pages/talk/chat_view.dart

@@ -110,10 +110,7 @@ class _ChatViewState extends State<ChatView> with RouteAware {
     if (state.currentToken != widget.room.token) return;
     final response = state.chatResponse;
     if (response == null) return;
-    var maxId = 0;
-    for (final m in response.data) {
-      if (m.id > maxId) maxId = m.id;
-    }
+    final maxId = response.data.map((m) => m.id).fold<int>(0, math.max);
     if (maxId == 0) return;
     _chatListBlocRef?.markRoomAsRead(widget.room.token, maxId);
     unawaited(_chatBlocRef!.sendServerReadMarker(widget.room.token, maxId));
@@ -230,21 +227,20 @@ class _ChatViewState extends State<ChatView> with RouteAware {
         ? _searchQuery
         : null;
 
+    final commonRead = int.parse(
+      response.headers?['x-chat-last-common-read'] ?? '0',
+    );
+
     final messages = <Widget>[];
     final chronologicalMatchIndex = <int, int>{};
     var lastDate = DateTime.now();
     for (final element in response.sortByTimestamp()) {
+      if (ChatSearchController.isHiddenSystemMessage(element)) continue;
+
       final elementDate = DateTime.fromMillisecondsSinceEpoch(
         element.timestamp * 1000,
       );
 
-      if (element.systemMessage.contains('reaction')) continue;
-      if (element.systemMessage.contains('poll_voted')) continue;
-      if (element.systemMessage.contains('message_deleted')) continue;
-      final commonRead = int.parse(
-        response.headers?['x-chat-last-common-read'] ?? '0',
-      );
-
       if (!elementDate.isSameDay(lastDate)) {
         lastDate = elementDate;
         messages.add(