fix(panel): wire search button to toggle spotlight

- Add on_clicked handler to search button in panel
- Add set_spotlight_toggle() method on Panel
- Connect spotlight.toggle in main.py after both are created

src/main.py

@@ -58,6 +58,7 @@ def main():
     panel = Panel()
     modusnoti = ModusNoti()
     spotlight = SpotlightWindow()
+    panel.set_spotlight_toggle(spotlight.toggle)
     deskwidget = Deskwidgets()
     dock = Dock()
     osd = OSDWindow()