debug(chatgui): add online status trace across full chain

- cs_is_peer_online: log found/init/links/online
- cs_on_peer_status_changed: log channel_count + found_in_channel
- cs_handle_welcome/cs_handle_channel_join: log before cs_post_channel_online
- MainWindow::onChannelPeersOnline: log cid+online
- ChannelList::setChannelPeersOnline: log search/rows, each row cid+match, SET or NOT FOUND
- ChannelList::loadChannels: log each added row cid+name

tools/chatgui/src/mainwindow.cpp

@@ -297,6 +297,7 @@ void MainWindow::onAutoConnectStatus(uint8_t status, uint16_t /*total_tried*/,
 void MainWindow::onChannelPeersOnline(const char* ch_id, int ch_id_len, uint16_t online) {
     if (m_channelList) {
         QString cid = QString::fromUtf8(ch_id, ch_id_len);
+        qDebug() << "MainWindow::onChannelPeersOnline cid=" << cid << "online=" << online;
         m_channelList->setChannelPeersOnline(cid, (int)online);
     }
 }