V130 - Direct account-folder native import (no character backups)

SAVE ACCOUNT CHARACTER keeps the working V125/V129 behavior:
- BG2 exports the selected character normally into the profile's literal `characters` working folder.
- The local router then moves only that newly exported CHR/BIO pair into `characters_<full account name>`.

IMPORT ACCOUNT CHARACTER no longer moves the account CHR/BIO files into `characters`.
- PREPARE ACCOUNT IMPORT asks the local router to expose `characters_<account>` through BG2's required literal path named `characters`.
- On Windows this is a directory junction, not a copy and not a per-character file move.
- The ordinary `characters` directory is renamed as one directory object to `_DRAKHYSYS_BASE_CHARACTERS` while the junction is active.
- The account CHR/BIO files remain physically in `characters_<account>` the entire time.
- After preparation, BG2's stock native `createCharScreen:OnImportCharacterButtonClick()` action is used unchanged to open the normal import list.
- SAVE, LOG OUT, CANCEL PREPARATION, router restart, or another safe reset removes the junction and restores the ordinary `characters` directory.

No account server is used. The local router only performs filesystem routing on the PC running BG2.
No character backups, duplicate copies, restore history, merge, synchronization, or automatic respawn are performed.
