Departments now carry a type (shot or asset) and own a list of task
types (e.g. Animation: blocking/primary_pass/second_pass, Composite:
first_pass/second_pass, plus a new Simulation department), additive to
the existing flat Custom Task Type system. When a task's type belongs
to a department, its department is derived and kept in sync server-side
across create/update paths; Task Type is now editable in the Task
Detail panel and Department options are filtered to the task's
shot/asset scope.
