V297 - Automatic account login release after exiting BG2

Root cause: V296's exit watcher only reset Activate and Disabled, while the
login UI also checks Existence. Existence=1 could persist after quitting,
preventing the same account from logging in until SETUP was rerun.

V297 resets all three flags when the owning BG2 process exits, and runs an
orphan-recovery check once all BG2 windows have been closed. The watcher now
uses 64-bit-correct Windows process handles and an operating-system mutex
instead of trusting a stale watcher PID file.

If a lock remains, close every BG2 window and run
RELEASE_STUCK_ACCOUNT_LOGIN.bat; it asks for the Documents profile and explicit
RELEASE confirmation. It never deletes characters or account registrations.

No changes to native Import, Export, account character folders, campaigns,
multiplayer, or per-account settings.

Install by closing BG2/InfinityLoader, extracting the archive, and running
SETUP_IN_GAME_ACCOUNTS.bat. Choose the correct Baldur.lua profile folder.
