Update position by external code

Performs a full update (replacement) of a position. All fields in the request body will replace the current values.

Business Rules:

• Role (externalCodeRole) is required and must exist

• Area (externalCodeArea) is required and must exist

• Parent position is optional - can be null for root position

• Employee assignment is optional (can be null to unassign)

• Employee can only be assigned to one position at a time

• Operation Unit (externalCodeOperationUnit) is optional (can be null to unassign)

• Set nullable fields to null to remove them