flake: Expose piket-active, piket-migrate

pyproject.toml

 piket-client = "piket_client.gui:main"
 piket-server = "piket_server.run:main"
 piket-seed = "piket_server.seed:main"
+piket-active = "piket_client.set_active:main"
+piket-migrate = "alembic.__main__:main"
 
 [build-system]
 requires = ["poetry-core"]