🐛(backend) fix dependencies conflicts

Upgrading Django to 5.1 created a severe issue.
Migrate and create-superuser jobs were failing.

The issue originated from the third party easy_thumbnail.
Please refer to the issue #641 on their repo.

This is the suggested workaround by @Miketsukami.

src/backend/meet/settings.py

@@ -275,6 +275,7 @@ class Base(Configuration):
     # Easy thumbnails
     THUMBNAIL_EXTENSION = "webp"
     THUMBNAIL_TRANSPARENCY_EXTENSION = "webp"
+    THUMBNAIL_DEFAULT_STORAGE_ALIAS = "default"
     THUMBNAIL_ALIASES = {}
 
     # Celery