chatgui: fix NodesPage truncated Node ID + add DB diagnostics

- NodesPage: show full 64-bit Node ID (hex16) instead of truncated 4 hex chars
- NodesPage: show diagnostic when DB handle is NULL (was silent return)
- DatabaseSettingsPage: show 'Database not connected' when DB handle is NULL
- DatabaseSettingsPage: add refreshStatus() called on tab select
- SettingsDialog: refresh Database tab on category change

tools/chatgui/src/databasesettingspage.cpp

@@ -127,6 +127,48 @@ DatabaseSettingsPage::DatabaseSettingsPage(DbManager* db, QWidget* parent)
     layout->addWidget(m_resultText);
 
     layout->addStretch();
+
+    if (!m_db || !m_db->m_db) {
+        m_statusLabel->setText("Database not connected");
+        m_statusLabel->setStyleSheet("font-size: 12px; font-weight: bold; color: red;");
+        m_quickBtn->setEnabled(false);
+        m_fullBtn->setEnabled(false);
+        m_optimizeBtn->setEnabled(false);
+        qWarning("DatabaseSettingsPage: DB not ready m_db=%p m_db->m_db=%p", (void*)m_db, m_db ? (void*)m_db->m_db : nullptr);
+    }
+}
+
+void DatabaseSettingsPage::refreshStatus() {
+    if (!m_db || !m_db->m_db) {
+        m_statusLabel->setText("Database not connected");
+        m_statusLabel->setStyleSheet("font-size: 12px; font-weight: bold; color: red;");
+        m_quickBtn->setEnabled(false);
+        m_fullBtn->setEnabled(false);
+        m_optimizeBtn->setEnabled(false);
+        return;
+    }
+    m_quickBtn->setEnabled(true);
+    m_fullBtn->setEnabled(true);
+    m_optimizeBtn->setEnabled(true);
+    const char* fname = sqlite3_db_filename(m_db->m_db, "main");
+    if (fname && fname[0]) {
+        QString dbPath = QString::fromUtf8(fname);
+        m_filePathLabel->setText(dbPath);
+        QFileInfo fi(dbPath);
+        if (fi.exists()) {
+            qint64 sz = fi.size();
+            if (sz < 1024) m_fileSizeLabel->setText(QString("%1 B").arg(sz));
+            else if (sz < 1024 * 1024) m_fileSizeLabel->setText(QString("%1 KB").arg(sz / 1024));
+            else m_fileSizeLabel->setText(QString("%1 MB").arg(sz / (1024.0 * 1024.0), 0, 'f', 2));
+            QFileInfo walFi(dbPath + "-wal");
+            if (walFi.exists()) {
+                qint64 wsz = walFi.size();
+                if (wsz < 1024) m_walSizeLabel->setText(QString("%1 B").arg(wsz));
+                else if (wsz < 1024 * 1024) m_walSizeLabel->setText(QString("%1 KB").arg(wsz / 1024));
+                else m_walSizeLabel->setText(QString("%1 MB").arg(wsz / (1024.0 * 1024.0), 0, 'f', 2));
+            } else { m_walSizeLabel->setText("n/a"); }
+        }
+    }
 }
 
 void DatabaseSettingsPage::setBusy(bool busy) {