refactor AdvancedSettingsDialog into own file and class

SongDialog.cpp

@@ -0,0 +1,50 @@
+#include "SongDialog.h"
+#include "ui_SongDialog.h"
+#include <QMessageBox>
+
+SongDialog::SongDialog(QWidget *parent, const QString &caption, const QString &lyrics)
+    : QDialog(parent),
+      ui(new Ui::SongDialog)
+{
+    ui->setupUi(this);
+    
+    // Set initial values if provided
+    if (!caption.isEmpty()) {
+        ui->captionEdit->setPlainText(caption);
+    }
+    if (!lyrics.isEmpty()) {
+        ui->lyricsEdit->setPlainText(lyrics);
+    }
+}
+
+SongDialog::~SongDialog()
+{
+    delete ui;
+}
+
+QString SongDialog::getCaption() const
+{
+    return ui->captionEdit->toPlainText();
+}
+
+QString SongDialog::getLyrics() const
+{
+    return ui->lyricsEdit->toPlainText();
+}
+
+void SongDialog::on_okButton_clicked()
+{
+    // Validate that caption is not empty
+    QString caption = getCaption();
+    if (caption.trimmed().isEmpty()) {
+        QMessageBox::warning(this, "Invalid Input", "Caption cannot be empty.");
+        return;
+    }
+    
+    accept();
+}
+
+void SongDialog::on_cancelButton_clicked()
+{
+    reject();
+}