Remove global service declarations and change to declarations upon usage. (#761)

* Remove global service declarations and change to declarations upon usage.

* Only load cava service if cava is enabled.

src/components/menus/notifications/helpers.ts

@@ -1,8 +1,9 @@
 import { bind, Variable } from 'astal';
 import AstalNotifd from 'gi://AstalNotifd?version=0.1';
-import { notifdService } from 'src/lib/constants/services';
 const { displayedTotal } = options.notifications;
 
+const notifdService = AstalNotifd.get_default();
+
 /**
  * Handles page boundaries for notifications.
  *