refactor(Loading): update Loading component import paths

- Changed import paths for the Loading component from "@/app/loading" to "@/components/loading" across multiple files to maintain consistency and improve modularity.
- Removed the Loading component definition from loading.tsx, simplifying the file structure.

src/components/Layouts/header/notification/notification-list.tsx

@@ -1,6 +1,6 @@
 "use client";
 
-import Loading from "@/app/loading";
+import Loading from "@/components/loading";
 import IsVisible from "@/components/ui/IsVisible";
 import { useGetMyNotifications } from "@/hooks/queries/useNotificationQueries";
 import { TNotificationDetailsResponse } from "@/lib/api/types/NotificationHistory";
@@ -21,7 +21,10 @@ const NotificationList = ({
     setUnreadNotificationCount(data?.data.length ?? 0);
   }, [data, isLoading]);
 
-  if (isLoading) return <Loading className={"p-6"} />;
+  if (isLoading)
+    return (
+      <Loading className="min-h-48 flex-none justify-center p-6" />
+    );
 
   return (
     <ul className="mb-3 max-h-[23rem] space-y-1.5 overflow-y-auto">