Adds hire/terminate staff actions and an upgradeStructure server action plus baseManagement components (employment card, hire dialog, staff roster, upgrade card) wired into the structure detail page.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
