fix: PCM copy, device name encoding, double shutdown

- playRawPcm: ma_audio_buffer_init_copy instead of ma_audio_buffer_ref (copies PCM)
- enumerateDevices: fromLocal8Bit instead of fromUtf8 for device names
- AudioRecorder: m_deviceStarted flag prevents double ma_device_uninit
- stopMicTest: delete instead of deleteLater to avoid deferred double shutdown

tools/chatgui/src/audiodevicesettingspage.cpp

@@ -214,7 +214,7 @@ void AudioDeviceSettingsPage::stopMicTest() {
     if (m_testRecorder) {
         m_testRecorder->stopRecording();
         m_testRecorder->shutdown();
-        m_testRecorder->deleteLater();
+        delete m_testRecorder;
         m_testRecorder = nullptr;
     }
     m_micTestActive = false;