wger: cross-tenant account deletion / deactivation / activation by gym.manage_gym + gym=None

Summary GHSA-mhc8-p3jx-84mm CVE-2026-43948 reported that wger's resetuserpassword and gympermissionsuseredit views in wger/gym/views/user.py performed a gym-scope authorization check using Django ORM object comparison if request.user.userprofile.gym != user.userprofile.gym which silently passes...