V205 - Exact account flags + strict Import/Export selector

LOGIN accountname:
- accountname Flag/Activate = 1
- accountname Disabled = 1
- the same account cannot log in again while either is 1

LOGOUT or EXIT:
- accountname Disabled = 0
- accountname Flag/Activate = 0
- only that account is changed

CHARACTERS:
- accountname selects only characters_<accountname>
- characters_<accountname> must contain the matching account identity flag
- Import rows are limited to CHR stems physically present in that account folder
- Export rows are read from that same active account folder and remain selectable for overwrite
- an empty account folder yields an empty Import/Export list

No automatic character backups or restoration. Delete Account remains disabled.
