feat(userarea.js): enhance file upload feedback

Enhanced the file upload feedback mechanism in `userarea.js` by
introducing a clearer, success indication and preparing for future
implementations where upload completion will trigger additional checks
against the API for resolution availability. This change brings a more
intuitive user experience during file uploads and lays groundwork for
next steps in upload handling, ensuring users are better informed of the
upload status in real-time.

- Imported `getElementById` for future feature expansion.
- Added a TODO comment as a placeholder for upcoming API check
functionality.

assets/js/userarea.js

@@ -1,7 +1,7 @@
 import "../scss/frontend.scss";
 import "../css/userarea.css";
 
-import { getCookie } from "./api";
+import { getCookie, getElementById } from "./api";
 
 import { Tab } from "bootstrap";
 import DataTable from "datatables.net-dt";
@@ -129,10 +129,11 @@ function uploadFile(file, progressBar, thumbnail) {
   xhr.onload = () => {
     if (xhr.status === 201) {
       const response = JSON.parse(xhr.responseText);
-      const thumbnailUrl = response.thumbnailUrl;
-      thumbnail.src = thumbnailUrl;
       progressBar.classList.add("bg-success");
       progressBar.textContent = "Success!";
+
+      // TODO: Check API until the first resolution is available
+
     } else {
       progressBar.classList.add("bg-danger");
       progressBar.textContent = "Error!";