[Fix] hs_helper: fix use-after-free in async hyperscan cache callbacks

[Fix] hs_helper: fix use-after-free in async hyperscan cache callbacks

Add proper refcounting to async compilation contexts to prevent
use-after-free when Redis callbacks are invoked multiple times
(timeout + response) or during worker termination.

- Add ref_entry_t to async context structures
- Use REF_RETAIN before async operations and REF_RELEASE in callbacks
- Add callback_processed flag to prevent double processing
- Save entry data before ev_run that might free pending arrays