fix: add destroy() and signal cleanup across widgets, fix settings window + menu regressions

P0 leak fixes: context/action menus destroyed on deactivate, config
callbacks unregistered in settings widgets, recorder and server signal
IDs stored and disconnected, bluetooth client closed and unsubscribed,
rfkill timer removed, seek timers cancelled, dropdown and options menus
freed, app name cache LRU-bounded.

Fix desktop 'Edit Widgets' and settings menu regressions by deferring
destroy out of Gtk signal handlers via GLib.idle_add.

Fix settings entry fields by connecting the activate signal explicitly
(Enter saves the value).

src/window/desktop/main.py

@@ -164,6 +164,7 @@ class DesktopWidgetWindow(WaylandWindow):
         self._dragging_eb: Gtk.EventBox | None = None
         self._drag_drop_success: bool = False
         self._input_rebuild_pending: bool = False
+        self._context_menu: Gtk.Menu | None = None
 
         self._root = Box(h_expand=True, v_expand=True)
         self._root.add(self._fixed)
@@ -296,7 +297,7 @@ class DesktopWidgetWindow(WaylandWindow):
         return False
 
     def _show_context_menu(self, event: Gdk.EventButton) -> None:
-        menu = Gtk.Menu()
+        menu = self._context_menu = Gtk.Menu()
 
         label_text = "Done Edit" if self._edit_mode else "Edit Widgets"
         edit_item = Gtk.CheckMenuItem(label=label_text)
@@ -304,9 +305,15 @@ class DesktopWidgetWindow(WaylandWindow):
         edit_item.connect("toggled", self._on_edit_toggled)
         menu.append(edit_item)
 
+        menu.connect("deactivate", self._on_context_menu_deactivate)
         menu.show_all()
         menu.popup_at_pointer(event)
 
+    def _on_context_menu_deactivate(self, menu) -> None:
+        if self._context_menu is menu:
+            self._context_menu = None
+        GLib.idle_add(menu.destroy)
+
     # edit mode
 
     def _on_edit_toggled(self, item) -> None: