[FIX][UX] (adminusers) : improve UX of 'user must change password' checkbox and password inputs

• [FIX][UX] (adminusers) : improve UX of 'user must change password' checkbox and password inputs

For : https://avan.tech/item138910

• On add user: password fields are required unless "user must change password" is checked
• On edit user:
  • If "user must change password" is toggled from active → inactive, a new password is required
  • If toggled from inactive → active (or left active), password inputs stay optional
• Prevents calling change_user_password() with an empty password