feat(members): split username/display_name, sync updates to authentik, add password reset API and refresh docs

backend/app/schemas/users.py

@@ -3,6 +3,7 @@ from pydantic import BaseModel
 
 class UserUpsertBySubRequest(BaseModel):
     sub: str
+    username: str | None = None
     email: str | None = None
     display_name: str | None = None
     is_active: bool = True