implement initial backend structure with authentication, user management, and database integration

backend/app/models/users.py

@@ -0,0 +1,17 @@
+"""Pydantic schemas for user management endpoints."""
+from pydantic import BaseModel, EmailStr
+
+
+class UserResponse(BaseModel):
+    id: str
+    email: str
+    role: str
+
+
+class UpdateUserRequest(BaseModel):
+    email: EmailStr | None = None
+    password: str | None = None
+
+
+class SetRoleRequest(BaseModel):
+    role: str