LMDB-based entity storage implementation using the heed crate.

This module provides an LMDB (via heed) implementation of the entity storage traits, mirroring the functionality of ents-sqlite but using LMDB as the underlying store.

Storage Layout

The implementation uses three LMDB databases:

• entities: Maps entity IDs to serialized entity JSON
• edges: Maps composite keys (source, sort_key, dest) to empty values
• meta: Stores metadata like the next entity ID