(refactor) Replace tokio::spawn_blocking with std thread for metadata preloading
- Use `std::thread` instead of Tokio's blocking pool to avoid potential thread starvation in async context
- Ensures long-running metadata loading does not block Tokio workers
- Update Cargo.lock packageversion
- Refactor DB initialization: move PRAGMA settings after table creation for correctness and clarity (WAL, cache size etc.)
- Add foreign key enforcement (`PRAGMAforeign_keys = ON`)
>- Reorder index creation to follow table definition
- Add new indexes: `idx_asset_last_used`, idx`_asset_hits`
>- Introduce indexed lazy_pk support with unique constraint on non-NULL values
> - Improve LRU index to use ASC ordering for efficient oldest-record lookup
