fix: use wildcard query when Redis index value is empty (#2069) (#2075)

* fix: use wildcard query when Redis index value is empty

When searching Redis with an empty filter, the query was generating
`@nl_state:{  }` which causes a syntax error at offset 10. This fix
uses `*` (match all) when the sanitized field is empty.

Also updates the test mock to handle wildcard queries and skip entries
without version fields (e.g., those created via HSET).

Fixes: Syntax error at offset 10 near state

* complete merge to comply with CI

* fix: resolve merge conflict in search_by_index_prefix

Merged main into fix-redis-query-syntax branch and resolved conflict
in the search_by_index_prefix method to work with RecoverablePool.

Changes:
- Extract Client from ClientWithPermit using client.client.clone()
- Pass sanitized_field as parameter to closure for proper ownership
- Maintain wildcard query fix (*) for empty filter values
- Maintain input sanitization security
,