V165 - PLAYER CHARACTER ISOLATION / ACCOUNT FLAGS / ONE LIVE EXPORT FILE

1. Each account is a player identity and owns a flag equal to the lowercase account name.
   Drakhysys -> flag drakhysys; Kronas -> flag kronas.
2. Login activates only that player flag and connects `characters` to characters_<flag>.
3. Logout deactivates the flag and disconnects the account character folder.
4. Import goes directly to BG2 Character File import. The Saved Game import-format choice is bypassed.
5. A character stable id (dra_1, dra_2, kro_1, ...) is permanently bound to its owner flag.
6. A character has one persistent export file. Background autosave overwrites that same stable id; it does not create a second player export.
7. Imported stable ids keep their binding. Legacy filenames receive one stable id and keep the same id thereafter.
8. The router rejects autosave when the active account flag does not match the character owner.
9. No automatic character backups, history copies, or deleted-character respawn are created.
