chat_settings: [chat] config section + live sync + fix test segfault

- New chat_setting.c/h: unified chat settings API (int/str getters)
- Config parser supports [chat] section, calls chat_setting_set per key
- chat_core exposes chat_core_set_setting / trampoline for GUI bridge
- chatgui: AudioDevice + Storage pages persist to [chat] config + live apply
- chatgui-android: ConfigProvider, NativeLib, headless handle chat settings
- MessageList: 200 msg limit, fixed saveChannelState via trampoline
- test_media_delivery_full: fix segfault at shutdown (mon() timer vs freed conns)

tools/chatgui/src/mainwindow.cpp

@@ -252,6 +252,8 @@ void MainWindow::setupBridgeCallbacks() {
         if (!lastCid.isEmpty()) {
             s_mainWindow->m_channelList->selectChannel(lastCid);
             s_mainWindow->m_accountList->setChannel(lastCid);
+            s_mainWindow->m_currentChannelId = lastCid;
+            s_mainWindow->m_messageList->loadChannel(lastCid);
         }
     });
 }