Switch to Python 3.12

https://redmine.teklia.com/issues/10050

Requires !2519 (merged)

Closes !1425, !1433 (closed), !1535 (closed), !2040 (closed), !2058 (closed), !2098 (closed), !2279 (closed)

Base image build: https://gitlab.teklia.com/arkindex/backend/-/jobs/707827