Add admin user management

app/repositories/portfolio_repository.py

@@ -4,12 +4,22 @@ from __future__ import annotations
 
 from typing import Protocol
 
-from app.domain.models import LedgerEntry, Portfolio, StrategySet
+from app.domain.models import LedgerEntry, Portfolio, StrategySet, User
 
 
 class PortfolioRepository(Protocol):
     def ping(self) -> None: ...
 
+    def get_user(self, user_id: str) -> User: ...
+
+    def list_users(self) -> list[User]: ...
+
+    def create_user(self, username: str, *, email: str | None = None) -> User: ...
+
+    def update_user(self, user_id: str, *, username: str | None = None, email: str | None = None) -> User: ...
+
+    def delete_user(self, user_id: str) -> None: ...
+
     def get(self, portfolio_id: str) -> Portfolio: ...
 
     def get_or_create(