Support the new API error format in StartProcess

Erwan Rouchet
2026-03-16T14:59:26Z

https://redmine.teklia.com/issues/11464

Requires backend#2038

[This error handling](https://gitlab.teklia.com/arkindex/frontend/-/blob/e3e7f5bec7cc4e199b85ec845a6e4e8873341993/src/views/Process/Configure.vue#L551) for `StartProcess` ne...