fix: hide call signaling and state events from chat timeline

Filter out org.matrix.msc3401.call.member, org.matrix.msc4075.rtc.notification,
m.call.*, m.room.member, and other state events from the chat timeline.
Users only see actual messages, not protocol noise.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/features/chat/data/chat_repository.dart

@@ -103,10 +103,34 @@ class ChatRepository {
     await room.requestHistory();
   }
 
+  /// Event types that should never appear in the chat timeline.
+  static const _hiddenEventTypes = {
+    'org.matrix.msc3401.call.member',
+    'org.matrix.msc4075.rtc.notification',
+    'com.famedly.call.member',
+    'm.call.invite',
+    'm.call.answer',
+    'm.call.hangup',
+    'm.call.candidates',
+    'm.call.reject',
+    'm.room.member',
+    'm.room.power_levels',
+    'm.room.join_rules',
+    'm.room.history_visibility',
+    'm.room.guest_access',
+    'm.room.create',
+    'm.room.topic',
+    'm.room.name',
+    'm.room.avatar',
+    'm.room.canonical_alias',
+    'm.room.encryption',
+  };
+
   Future<List<MessageModel>> _mapTimeline(Timeline timeline, Room room) async {
     final myUserId = _client.userID ?? '';
     final models = <MessageModel>[];
     for (final e in timeline.events) {
+      if (_hiddenEventTypes.contains(e.type)) continue;
       models.add(_toModel(e, timeline, myUserId));
     }
     // Matrix SDK timeline.events is newest-first. Keep that order because