refactor: drive UI from service signals, drop redundant polling

- bluetooth.py / wifi.py: remove 5s periodic refresh timers; rely on
  service `changed`/`device-added`/`device-removed`/`notify` signals
- expanded_player.py: remove 500ms metadata poll; rely on
  `meta-change`/`artwork-change` signals
- player.py (notch): connect previously dangling `artwork-change` handler
- popup_win.py: silence harmless "nothing connected" warning on destroy()

No behaviour change; eliminates dead timers and log spam.

src/shared/window/popup_win.py

@@ -100,15 +100,17 @@ class PopupWindow(WaylandWindow):
             try:
                 self._pointing_widget.disconnect_by_func(self.do_handle_size_allocate)
             except Exception as e:
-                logger.warning(
-                    f"[popup_win] self._pointing_widget.disconnect_by_func(self.do_handle_s... failed: {e}"
-                )
+                if "nothing connected" not in str(e):
+                    logger.warning(
+                        f"[popup_win] self._pointing_widget.disconnect_by_func(self.do_handle_s... failed: {e}"
+                    )
         try:
             self.disconnect_by_func(self.do_handle_size_allocate)
         except Exception as e:
-            logger.warning(
-                f"[popup_win] self.disconnect_by_func(self.do_handle_size_allocate) failed: {e}"
-            )
+            if "nothing connected" not in str(e):
+                logger.warning(
+                    f"[popup_win] self.disconnect_by_func(self.do_handle_size_allocate) failed: {e}"
+                )
         super().destroy()
 
     def do_calculate_edges(self):