Inconsistent Persistence Layers* #153
Description
The backend architecture is confused about its primary data store:
- While most routes in server.js use MongoDB via the Batch.js model, there is a completely separate in-memory store in BatchStore.js initialized with sample data.
- This duplication can lead to scenarios where some parts of the app show stale or inconsistent data if they inadvertently use the in-memory store instead of the database.