Authenticated Movary User Can Self-Escalate to Administrator via PUT /settings/users/{userId} by Setting isAdmin=true

Movary is a self hosted web app to track and rate a user's watched movies. Prior to version 0.71.1, an ordinary authenticated user can escalate their own account to administrator by sending `isAdmin=true` to `PUT /settings/users/{userId}` for their own user ID. The endpoint is intended to let a user edit their own profile, but it updates the sensitive `isAdmin` field without any admin-only authorization check. Version 0.71.1 patches the issue.