Total storage' value remains the same after uploading or deleting a file

Observed behavior

Encountered while testing https://github.com/learningequality/studio/pull/3044: The 'Total storage used' value remains the same after uploading or deleting a file.

Expected behavior

The 'Total storage used' value should update correctly after uploading or deleting a file.

User-facing consequences

Users won't be able to know what is the actual 'Total storage used' value.

Additional information

Steps to reproduce the issue

Case: File upload and user storage status

1. Open an editable channel
2. Click Add and Upload files
3. Note your current Total storage used
4. Upload a file and finish up editing the uploaded file's details
5. Click Add and Upload files again
6. Confirm that your Total storage used has updated properly

Case: Adding and deleting a file updates publish channel size

1. Create a new channel
2. Click Add and Upload files to upload a small file
3. Click Publish
4. Observe the channel size shown in the Publish modal
5. Close the Publish modal
6. Click Add and Upload files to upload a large file (like a video)
7. Allow your browser to finish syncing (wait ~30 seconds)
8. Click Publish
9. Verify the channel size has increased in the Publish modal
10. Close the Publish modal
11. Delete the large file
12. Click Publish
13. Verify the channel size has decreased in the Publish modal

Usage Details

• OS: Windows 10
• Browser: Chrome, Firefox
• URL: https://hotfixes.studio.learningequality.org/

Start by reproducing the upload and deletion cases in the issue, checking the Total storage used value and the channel size in the Publish modal after synchronization. Trace the entry points for file upload, file deletion, storage status, and publishing, then add coverage showing both values increase and decrease correctly.