Keep the server tab strip in step with theme switches

The strip is out of the component tree while one server is open, so a
look-and-feel switch missed it and it came back in the old theme's colours.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ts3-client/swing/src/main/java/com/ts3client/ui/ServerTabPane.java

@@ -9,6 +9,7 @@ import javax.swing.JComponent;
 import javax.swing.JLabel;
 import javax.swing.JPanel;
 import javax.swing.JTabbedPane;
+import javax.swing.SwingUtilities;
 import java.awt.BorderLayout;
 import java.awt.Component;
 import java.awt.Dimension;
@@ -60,6 +61,16 @@ final class ServerTabPane extends JPanel {
         dragReorder.attach(tabbed);
     }
 
+    /**
+     * The tab strip is out of the component tree while a single server is open, so a
+     * look-and-feel switch would miss it and leave it in the old theme's colours.
+     */
+    @Override
+    public void updateUI() {
+        super.updateUI();
+        if (tabbed != null && tabbed.getParent() == null) SwingUtilities.updateComponentTreeUI(tabbed);
+    }
+
     /** Drags a tab from one position to another, keeping the current selection on screen. */
     private void moveTab(int from, int to) {
         if (from < 0 || to < 0 || from >= tabs.size() || to >= tabs.size() || from == to) return;