V131 - Load account characters, then use native BG2 Import (no backups)

SAVE ACCOUNT CHARACTER keeps the working V125 behavior.

Character creation screen:
1. The former BIOGRAPHY button position is now LOAD ACCOUNT CHARACTERS.
2. LOAD moves only the logged-in account CHR/BIO files from characters_<account> into BG2's normal characters folder.
3. The same button changes to ACCOUNT CHARACTERS READY after the local mover confirms completion.
4. IMPORT ACCOUNT CHARACTER is a separate button and calls BG2's original createCharScreen:OnImportCharacterButtonClick() directly.
5. No filesystem operation runs from the IMPORT button itself.
6. Staged source files remain available while BG2 imports, then return to the account folder at a later safe SAVE, LOG OUT, or router restart.

No character backups, copies, restore history, merge, synchronization, or respawn.
