chatgui: add sound playback via miniaudio (MP3 notification sounds)

- SoundManager singleton wraps ma_engine + ma_sound (non-blocking, background thread)
- MP3 files embedded in QRC, decoded to PCM at startup with MA_SOUND_FLAG_DECODE
- miniaudio.h (MIT) in lib/, IMPLEMENTATION in separate miniaudio_impl.c
- Sound settings page in SettingsDialog: enable/disable, volume slider (0-100%)
- Config keys [gui] sound_enabled, sound_volume
- Incoming messages trigger msg_incoming.mp3 sound

tools/chatgui/src/sound_manager.cpp

@@ -0,0 +1,124 @@
+#include "miniaudio.h"
+
+#include "sound_manager.h"
+#include <QFile>
+#include <QDebug>
+
+SoundManager* SoundManager::instance() {
+    static SoundManager s;
+    return &s;
+}
+
+SoundManager::~SoundManager() { shutdown(); }
+
+bool SoundManager::init() {
+    if (m_initialized) return true;
+
+    ma_engine* engine = new ma_engine;
+    ma_result result = ma_engine_init(NULL, engine);
+    if (result != MA_SUCCESS) {
+        qWarning("SoundManager: ma_engine_init failed (%d)", result);
+        delete engine;
+        return false;
+    }
+    m_engine = engine;
+    m_initialized = true;
+    qDebug("SoundManager: initialized");
+    return true;
+}
+
+void SoundManager::shutdown() {
+    if (!m_initialized) return;
+
+    for (auto it = m_sounds.begin(); it != m_sounds.end(); ++it) {
+        if (it->sound) {
+            ma_sound_uninit(it->sound);
+            delete it->sound;
+        }
+    }
+    m_sounds.clear();
+
+    if (m_engine) {
+        ma_engine_uninit(m_engine);
+        delete m_engine;
+        m_engine = nullptr;
+    }
+    m_initialized = false;
+    qDebug("SoundManager: shutdown");
+}
+
+void SoundManager::setEnabled(bool enabled) {
+    m_enabled = enabled;
+    qDebug("SoundManager: enabled=%d", enabled);
+}
+
+bool SoundManager::isEnabled() const { return m_enabled; }
+
+void SoundManager::setVolume(float volume) {
+    if (volume < 0.0f) volume = 0.0f;
+    if (volume > 1.0f) volume = 1.0f;
+    m_volume = volume;
+    for (auto it = m_sounds.begin(); it != m_sounds.end(); ++it) {
+        if (it->sound)
+            ma_sound_set_volume(it->sound, m_volume);
+    }
+}
+
+float SoundManager::volume() const { return m_volume; }
+
+bool SoundManager::loadSound(const QString& name, const QString& qrcPath) {
+    if (!m_initialized) {
+        qWarning("SoundManager: not initialized, cannot load %s", qPrintable(name));
+        return false;
+    }
+    if (m_sounds.contains(name)) {
+        qWarning("SoundManager: sound '%s' already loaded", qPrintable(name));
+        return false;
+    }
+
+    QFile f(qrcPath);
+    if (!f.open(QIODevice::ReadOnly)) {
+        qWarning("SoundManager: cannot open %s", qPrintable(qrcPath));
+        return false;
+    }
+    QByteArray mp3Data = f.readAll();
+    f.close();
+
+    ma_decoder_config decConfig = ma_decoder_config_init_default();
+    ma_decoder decoder;
+    ma_result result = ma_decoder_init_memory(mp3Data.constData(), mp3Data.size(), &decConfig, &decoder);
+    if (result != MA_SUCCESS) {
+        qWarning("SoundManager: ma_decoder_init_memory failed for %s (%d)", qPrintable(name), result);
+        return false;
+    }
+
+    LoadedSound ls;
+    ls.sound = new ma_sound;
+    result = ma_sound_init_from_data_source(m_engine, (ma_data_source*)&decoder.ds,
+                                             MA_SOUND_FLAG_DECODE,
+                                             NULL, ls.sound);
+    ma_decoder_uninit(&decoder);
+
+    if (result != MA_SUCCESS) {
+        qWarning("SoundManager: sound init failed for %s (%d)", qPrintable(name), result);
+        delete ls.sound;
+        return false;
+    }
+
+    m_sounds.insert(name, ls);
+    qDebug("SoundManager: loaded '%s' from %s (%lld bytes)",
+           qPrintable(name), qPrintable(qrcPath), (long long)mp3Data.size());
+    return true;
+}
+
+void SoundManager::play(const QString& name) {
+    if (!m_enabled || !m_initialized) return;
+
+    auto it = m_sounds.find(name);
+    if (it == m_sounds.end()) return;
+
+    ma_sound* s = it->sound;
+    ma_sound_stop(s);
+    ma_sound_seek_to_pcm_frame(s, 0);
+    ma_sound_start(s);
+}