feat(Index): make Index send + sync thread safe

**Is your feature request related to a problem? Please describe.**
N/A

**Describe the solution you'd like**
Just make Index: Send + Sync

**Describe alternatives you've considered**
I created my own custom Index Type

Find the Index type definition in the codebase, likely in a file like src/index.rs or similar. Understand its current fields and any internal mutability patterns (like RefCell, Mutex) that may prevent Send + Sync. Review Rust's Send and Sync traits and the project's threading model. Check for any existing tests related to Index or concurrency to ensure changes don't break functionality.

Escrita pelo modelo de indexação a partir do texto da issue.