simplify: dedupe boilerplate and remove dead code across all layers

lib/view/pages/talk/data/chat_search_controller.dart

@@ -10,6 +10,14 @@ class ChatSearchMatch {
 }
 
 class ChatSearchController {
+  /// System messages that are folded into other bubbles (reactions, poll
+  /// votes, deletions) and therefore never rendered nor searched as their own
+  /// entry.
+  static bool isHiddenSystemMessage(GetChatResponseObject element) =>
+      element.systemMessage.contains('reaction') ||
+      element.systemMessage.contains('poll_voted') ||
+      element.systemMessage.contains('message_deleted');
+
   static List<ChatSearchMatch> findMatches(
     GetChatResponse response,
     String query,
@@ -19,9 +27,7 @@ class ChatSearchController {
 
     final matches = <ChatSearchMatch>[];
     for (final element in response.sortByTimestamp()) {
-      if (element.systemMessage.contains('reaction')) continue;
-      if (element.systemMessage.contains('poll_voted')) continue;
-      if (element.systemMessage.contains('message_deleted')) continue;
+      if (isHiddenSystemMessage(element)) continue;
 
       final haystackText = RichObjectStringProcessor.parseToString(
         element.message,