See post 3 here:

https://forum.seafile.com/t/seafile-docker-403-csrf-error-after-logon/17474/2

Several things to try here

https://github.com/haiwen/seafile/issues/2707

Slightly off topic but what proton subscription do you have? Proton Unlimited is email + storage via Drive with 500GB and VPN for $12.99/mo if paying monthly, otherwise it’s $10/mo or $8/mo if you pay 1 or 2 years in advance, respectively.

Separate DB containers for each service. Easier, more secure, and less messy. The overhead impact is trivial.