- Replace use case-based client deletion with direct service call
- Introduce DeleteClientInput struct for deletion parameters
- Remove delete_client_use_case from UseCaseBundle and factories
- Update ClientService trait and implementation to accept
  DeleteClientInput

Replace use case structs with input structs and update core service
trait and implementation to support new handler signatures.

- Remove use-case and orchestrator modules from core
- Implement domain service traits in FerriskeyService
- Update API handlers to call domain services instead of use-cases
- Move credential and user logic into service trait impls
- Simplify startup logic to use CoreService trait
- Remove unused service and strategy modules
- Update imports and wiring throughout application and domain layers