chatgui: channel sorting by name or last message time with preview

- Add last_msg_at column to channels table
- Update last_msg_at on every message insert (send/receive)
- Parameterize getChannels() with ChannelSortMode enum (Alphabetical/Recent)
- Add getChannelLastMessage() for preview text in channel list
- Add sorting combo to Profile settings page (stored in ui_state)
- Reload channels on message receive when sort is recent

tools/chatgui/src/settingsdialog.cpp

@@ -18,6 +18,7 @@ extern "C" {
 #include <QLabel>
 #include <QFormLayout>
 #include <QLineEdit>
+#include <QComboBox>
 #include <QFile>
 #include <QTextStream>
 
@@ -69,6 +70,15 @@ SettingsDialog::SettingsDialog(const QString& configPath, DbManager* db, UtunNod
         "QLineEdit { border: 1px solid palette(mid); border-radius: 4px;"
         " padding: 6px 10px; font-size: 13px; background: palette(base); }");
     profLayout->addRow(nameLabel, m_nicknameEdit);
+
+    auto* sortLabel = new QLabel("Channel sorting:", profilePage);
+    m_sortCombo = new QComboBox(profilePage);
+    m_sortCombo->addItem("Alphabetical (A-Z)");
+    m_sortCombo->addItem("Recent Activity");
+    m_sortCombo->setStyleSheet(
+        "QComboBox { border: 1px solid palette(mid); border-radius: 4px;"
+        " padding: 6px 10px; font-size: 13px; background: palette(base); }");
+    profLayout->addRow(sortLabel, m_sortCombo);
     m_pages->addWidget(profilePage);
 
     // Network page
@@ -124,6 +134,10 @@ SettingsDialog::SettingsDialog(const QString& configPath, DbManager* db, UtunNod
 
     // Load current values
     loadProfileFromConfig(m_configPath);
+    if (db) {
+        int sortMode = db->getUiStateInt("channel_sort", 0);
+        m_sortCombo->setCurrentIndex(sortMode == 1 ? 1 : 0);
+    }
     m_networkPage->loadFromConfig(m_configPath);
     m_soundPage->loadFromDb();
     m_categoryList->setCurrentRow(0);
@@ -189,6 +203,21 @@ void SettingsDialog::onSave() {
     f.close();
 
     m_networkPage->saveToConfig(m_configPath);
+
+    /* save channel sort preference to ui_state */
+    {
+        const char* key = "channel_sort";
+        QByteArray val = QByteArray::number(m_sortCombo->currentIndex());
+        size_t klen = strlen(key), vlen = (size_t)val.size();
+        size_t total = klen + 1 + vlen + 1;
+        if (total <= 256) {
+            void* arg = u_malloc(total);
+            memcpy(arg, key, klen + 1);
+            memcpy((char*)arg + klen + 1, val.constData(), vlen + 1);
+            gui_bridge_post_uasync_fn(chat_core_save_ui_state_trampoline, arg);
+        }
+    }
+
     m_soundPage->applyAndSave();
     accept();
 }