DRAKHYSYS V169 - ACCOUNT-BOUND READ/WRITE EXPORT FILTER - NO BACKUPS

Rules:
- Login activates exactly one account/player flag and mounts only characters_<account> as BG2's characters path.
- Logout clears the active flag and disconnects that account folder.
- Import Character remains the working direct Character File flow and stays account-isolated.
- Import Saved Game and pregenerated non-account routes remain disabled.
- Export Character opens BG2's normal native CHARACTER_EXPORT screen.
- The export list is filtered to character stems explicitly bound to the active account by the router.
- Legacy aliases (for example an older DRA/JENNIE filename) remain readable only when that alias resolves to a stable id owned by the active account.
- Other-account and unbound stock/global export names are hidden from the Export list.
- The current player character can save/replace only its own stable account id (dra_1, kro_1, etc.).
- The export filename field remains locked, so it cannot be redirected to another account character or arbitrary filename.
- Re-export uses BG2's native Done/overwrite behavior against that same one stable file.
- No automatic CHR/BIO backup copies, history files, or deleted-character restoration are added.
