Great news: everything should now be working fine again on this instance, including media upload.
These last two to free days have been difficult but everything should be back working normally now.
If you see anything wrong, please contact this account or, more preferably, @TheKinrar (or send an email to contact@thekinrar.fr).
We'll investigate the details of what happened and take measures to prevent this from happening again later today. Stay tuned. :)
Thank you everyone. 🎉